Thanks for the reply Wastewater, sorry for the delayed response. That OP was terrible, I apologize, I shouldn't try to post long text from my phone.
Good description, and details, pertaining to "Here is where I am".
Lighting? I don't think this was mentioned (what type of light source are you using, along with photo-periods/how long your lights are on). Also maintenance; water change schedule if any? You mentioned the tank being started up and completely cycled, but in reality: it is still a very new/young set-up. "Plants look moderate... others are struggling... new growth and root growth looks great... it's the older established plants that look weak or yellowing". I lean towards that 'old-school' phrase: if it ain't broke, don't fix it.
Bulb is a ZooMed Flora Sun, as it seemed the best short term moderately priced bulb that would fit the T8 fixture that I have. Bulb is on a glass canopy ~1" over the water's surface, ~20" to the substrate from the surface. Still researching the long term answer. I am leaning heavily towards the satellite plus pro fixture. Pricey, but seems like it has the most options as I figure out what I really need and like. Photo period varies a bit, based on when who turns the light off. turned on about 7:30-8 a.m. daily, off 8:30-11 p.m. It has been getting turned off daily before 9:00 p.m. the last week or so.
As far as maintenance. I've done 3 5gal water changes so far since the tank finished it's initial cycling. Mostly for the purpose of adding in RO water to reduce the overall hardness/gH. I normally do water changes to reduce nitrates, and here I have next to none, and actually want more, lol. It is a very new setup, and I am aware of that. The most recent hiccup since the original post, I increased the feeding a bit, especially with pellets overnight (NLS community formula), trying to get the nitrates (and possibly phosphates) up a bit, and to make sure the new zebra pleco has food at night since he's still quite shy. Backfire on that is I seem to have stressed the biological filter a bit, ~20-25 nitrites. So I need to wait that out.
As far as "if it ain't broke don't fix it", I agree 100%. My problem here is simply, I can't tell if anything is broken or not with regards to the plants. I also got a phosphate test kit today, looks to be around 25ppm.
Give it a bit of time, observe and keep doing what you are doing. "New growth & root growth looks great" is a good thing! IMO, a moderately lit tank with fairly undemanding plants, should do fine with 12-19ppm CO2. You have also started dosing a few plant nutrients, so time can become your friend (a lean dosing routine may be best initially). Personally, I might of held back on your initial *fauna-stocking-rate* for awhile, but that is just me (it is hard not 'caving-in' to the wife and kids).
Thanks, that is the plan. Just trying to keep an eye out for problems, since I am not even sure what a "real" problem is. The fauna stocking is due to the fact that this is intended primarily fish tank, with the long term goal to grow out a ghost knife fish. I always wanted to learn the true ins and outs of a planted tank, so I am using it my learning project, also being as once we set up a larger tank for the ghost long term, I'd like to have that planted as well, so you know, learn on a smaller scale. I should also add, this whole setup was a Xmas present to the wife for said ghost knife, so that is the true purpose.
On the Co2, doing a calculation today, I got 0.8ppm (based on 6.9pH, 4kH, 35gal). Of course that is all based on the API test kits, and my interpretation of the colors, so more than a bit of an error range. I put a tiny amount of SeaChem acid buffer in the tank (< 1/4tsp). That should drop the pH a touch, and according to SeaChem at least, should convert some of the carbonates into dissolved Co2. I am looking heavily into the DIY-type Co2 kits, with citric acid and 2 2 liter bottles, etc. But still trying to get my head around all the parts of those systems. Can you even use a "reactor" that fully mixes the co2 into the water in the return line of a filter with a DIY type system?
I would definitely monitor water parameters, observe plant growth, be on the watch for excessive algae growth, and observe general fish behavior/health very closely for the next couple of months. If things start going south within this window of time, you can begin tweaking/trouble-shooting to correct problems (and/or damage control) and hopefully prevent future problems by figuring out what a good 'balance' would be for "your" tank. If you have an opportunity, please share some pictures of your set-up.
That is the plan. But again, with the plants anyways, what are strong signs of problems? Yellowing leaves aren't that bad of a sign? Or is that because the tank is new? etc etc. I'll post a few pics soon.