Thanks for the suggestions and encouragement, folks!
@Asteroid, I took your advice and continued dosing ferts. My photoperiod is now a 1-hour sunrise, 4 hours at full strength, and a 1-hour sunset (I need to find out what strength sunrise and sunset are on the Fluval 3.0 - I'm pretty sure it's <50%). I've also been doing 50% water changes every other day for almost a week now.
Despite these changes, the algae has continued to spread. The ammonia has dropped from 4 PPM a few days ago to 0.25, but nitrites still register at 5.0 and nitrate is at 0, so clearly, there's still some progress to be made in cycling the tank. I dosed Seachem Stability to try to move things along, not out a desire to speed up the cycle, but out of a desire to get the ammonia under control to slow the algae. I've read mixed reviews on the stuff, particularly in planted tanks, but ultimately I decided it couldn't hurt. This was 3 days ago, so I'll give it a few more days to see how it's moved along.
Today, however, the algae spread from the hardscape to affecting some of the plants, something I was really hoping wouldn't happen. In response, I gave @DarkCobra's One-Two Punch a shot this afternoon. I removed the filter socks and media and added 100 ml of H2O2. DarkCobra revised the original recommended amount from 4 to 2 tbsp per gallon. Considering I don't have any fauna to worry about, I figured I'd split the difference and 100 ml works out to be pretty close to 3 tbsp per gallon (the hardscape takes up about 8 or 9 gallons of space, so I'm basing this on an estimate of 22 gallons of water). I also added the 200 GPH fountain pump that I have to create more flow which was a terrible decision with plants that have only week and a half's worth of roots. I blew plants all over the place! That said, it turns out I had algae in places I had no idea I had algae! The false pearling really highlighed it:
.
After 30 minutes I did a 50% water change and dosed 12 ml of Metricide 14 (about triple an initial dose of Seachem Excel). I built a super-simple water change setup over the weekend using a leftover 5-gallon homebrewing fermenter bottle, a 15 gallon, wheeled rubbermaid container and a pond pump which makes dosing really easy. This is probably overkill at this stage, but when I've eventually got shrimp in the tank, I can easily pre-filter the siphon and mix water in the rubbermaid to keep tank parameters (temp, TDS, etc.) consistent through water changes.
Lastly, the reduced photoperiod has really slowed the growth of the plants, but most of them are doing really well regardless. The Vals have sent out a lot of runners, the Ludwigia Senegalensis already needed a significant trim, and the AR mini and micranthum umbrosum have grown substantially. The Monte Carlo continues to put out new leaves but still hasn't spread and some of it has died off completely. I think that it's going to turn the corner here shortly though.
The Rotala Macaranda has struggled the most by far. At least 75% of it has wilted and died off now. I have no idea what's holding it back so much. I removed all of the decaying tissue today and temporarily moved what was left to the front of the tank where it'll be easier to keep an eye on and where there is no shade whatsoever from the hardscape. If it doesn't turn around in the next few days I'm going to have to pull it and find an alternative for that portion of the scape.
Ultimately, I think @Asteroid was right - I wasn't preventative enough from the very beginning. After the initial planting, I didn't do a water change for 5 or 6 days which is where things probably got out of hand. Perhaps I didn't run into this with previous Aqua Soil tanks because they were extremely heavily stocked with plants from the get-go. The scape I have in my head for this tank relies heavily on the MC which just hasn't taken off like I expected it to. The additional MC I ordered should be here in 2 or 3 days, so hopefully that gives the flora the boost that it needs.
@Asteroid, I took your advice and continued dosing ferts. My photoperiod is now a 1-hour sunrise, 4 hours at full strength, and a 1-hour sunset (I need to find out what strength sunrise and sunset are on the Fluval 3.0 - I'm pretty sure it's <50%). I've also been doing 50% water changes every other day for almost a week now.
Despite these changes, the algae has continued to spread. The ammonia has dropped from 4 PPM a few days ago to 0.25, but nitrites still register at 5.0 and nitrate is at 0, so clearly, there's still some progress to be made in cycling the tank. I dosed Seachem Stability to try to move things along, not out a desire to speed up the cycle, but out of a desire to get the ammonia under control to slow the algae. I've read mixed reviews on the stuff, particularly in planted tanks, but ultimately I decided it couldn't hurt. This was 3 days ago, so I'll give it a few more days to see how it's moved along.
Today, however, the algae spread from the hardscape to affecting some of the plants, something I was really hoping wouldn't happen. In response, I gave @DarkCobra's One-Two Punch a shot this afternoon. I removed the filter socks and media and added 100 ml of H2O2. DarkCobra revised the original recommended amount from 4 to 2 tbsp per gallon. Considering I don't have any fauna to worry about, I figured I'd split the difference and 100 ml works out to be pretty close to 3 tbsp per gallon (the hardscape takes up about 8 or 9 gallons of space, so I'm basing this on an estimate of 22 gallons of water). I also added the 200 GPH fountain pump that I have to create more flow which was a terrible decision with plants that have only week and a half's worth of roots. I blew plants all over the place! That said, it turns out I had algae in places I had no idea I had algae! The false pearling really highlighed it:

After 30 minutes I did a 50% water change and dosed 12 ml of Metricide 14 (about triple an initial dose of Seachem Excel). I built a super-simple water change setup over the weekend using a leftover 5-gallon homebrewing fermenter bottle, a 15 gallon, wheeled rubbermaid container and a pond pump which makes dosing really easy. This is probably overkill at this stage, but when I've eventually got shrimp in the tank, I can easily pre-filter the siphon and mix water in the rubbermaid to keep tank parameters (temp, TDS, etc.) consistent through water changes.

Lastly, the reduced photoperiod has really slowed the growth of the plants, but most of them are doing really well regardless. The Vals have sent out a lot of runners, the Ludwigia Senegalensis already needed a significant trim, and the AR mini and micranthum umbrosum have grown substantially. The Monte Carlo continues to put out new leaves but still hasn't spread and some of it has died off completely. I think that it's going to turn the corner here shortly though.
The Rotala Macaranda has struggled the most by far. At least 75% of it has wilted and died off now. I have no idea what's holding it back so much. I removed all of the decaying tissue today and temporarily moved what was left to the front of the tank where it'll be easier to keep an eye on and where there is no shade whatsoever from the hardscape. If it doesn't turn around in the next few days I'm going to have to pull it and find an alternative for that portion of the scape.
Ultimately, I think @Asteroid was right - I wasn't preventative enough from the very beginning. After the initial planting, I didn't do a water change for 5 or 6 days which is where things probably got out of hand. Perhaps I didn't run into this with previous Aqua Soil tanks because they were extremely heavily stocked with plants from the get-go. The scape I have in my head for this tank relies heavily on the MC which just hasn't taken off like I expected it to. The additional MC I ordered should be here in 2 or 3 days, so hopefully that gives the flora the boost that it needs.