I think what's happening is that you're suffocating your fish with CO2. You mentioned using Aquasoil, which will lower your KH over time. This isn't a bad thing, but it is throwing off your CO2 controller. Here's what I believe to be going on:
When you perform a water change on your tank, you're effectively 'setting' the initial levels--all is good. Over the next 3-5 days, your KH is dropping and your CO2 controller is pumping in more CO2. You would think that the pH would drop as well and shut it off. Well, yes and no. When you lower your KH, the pH doesn't always follow; what's happening is the lower KH levels is allowing the CO2 to dissolve much easier into the water. This is a good thing for plants, but not so much for fish. The pH will eventually catch up, but not fast enough for fish. This is where people get confused about the CO2 chart and why the chart isn't very effective. I had the opposite effect using a substrate (Seachem's Onyx) when trying get enough CO2 into the water. The KH kept raising, making it more difficult day by day to get enough CO2 into the water.
The cure: There are several ways to approach this. Ideally, the lower the KH the better, but it needs to be stable. pH doesn't matter, so don't worry about it. For now, I would discontinue using your CO2 controller and either run CO2 24/7 or use the solenoid to shut it off at night. Perform your water change (or leave things be), and find out how long it takes for the KH to drop to its lowest level and remains stable--you'll want to test KH daily and chart it on a post-it or something. It can even be at zero, but I suspect it will reach 3-5dKH and stop. At this point, things are stable. You can set your bubble rate on your CO2 system and not worry when leaving for work.
The tricky part is this: water changes. A time will come when you need to do some maintenance and change some water. When you use tap water, your KH will rise again, and chances are, you'll see some algae because the higher KH will make it more difficult to dissolve CO2 into the water. So, you can note the amount of water you changed and the level the KH raised to, and increase the CO2. Now of course, you know what's going to happen--the KH lowers and you'll OD your fish on CO2. You'll need to adjust your CO2 daily. If you've charted it all, you can predict things from day to day as long as you've kept things stable. I think you see where I'm going with this.
The good news is, eventually the Aquasoil will stop dropping your KH so much, but that could take 3-5 months or so. Another idea would be to place your new rock into the tank after your water change and remove it when the Aquasoil stops influencing your KH. This could be the very simple answer, but I wanted to state the above so you understand what's going on. Regardless, it's not your pH or GH, and I'd discountinue the use of your CO2 controller for now. Since you're in the Houston area, I can tell you your GH is high, very high, anywhere from 13-18+dGH. I wouldn't bother testing for it or even worrying about it. I think when you stabilize your water params, you'll see your fish health improve greatly. Stress can make them succeptible to all kinds of diseases.