Time for an update. It has proven difficult to grow plants successfully in New Orleans’ very alkaline and hard water, even with CO2 injection. Several plants died or faded away, including: Alternanthera Reineckii (regular and mini), Nasea Pedicellata Golden, Rotala Macrandra "narrow leaf," and Rotala Wallichi. I also had a major outbreak of BBA. However, after getting a pH meter and doing the 1 full point pH drop test, I realized that I was not injecting enough CO2.
Your problem was probably not CO2. Instead it was caused by a fertilizer that is incompatible with your ph and alkalinity. In your first post you stated your PH was 7.7. The iron DTPA in your fertilizer works best with a PH of 7.5 or less. Above 7.5 it rusts and becomes unusable by plants. When you increased your CO2 the PH topped and that help keep iron available in your tank.
You Also list your KH 113. Many of the ingredients in your fertilizer are sulfates. Sulfates react with kH causing many of the nutrients in your fertilizer to oxidize rendering them unabalable for plants.
the 3rd issue i see with your fertilizer is it uses Sodium molybdate. The sodium will also react with your sulfate ingredients in the bottle. resulting in insoluble molybdate which is unusable to plants. I made my own sulfate recipe and notices all of these issues.
I would recommend switching from thrive to G
LA iron DTPA EDTA micro fertilizer. it is chelated and has iron DTPA that is stable up to a PH of 7.5. IT is also Chelated so KH will not effect it. and the molybdenum is also Chelated so it will not react with other ingredients. It also has a better ballance of nutrients. My RO water tanks a normal PH of 7 so Iron DTPA works fine in my tanks.
Unfortunately it doesn't have nitrogen, potassium, phosphate, and magnesium. However you can use
this fertilizer calculator to determine exactly how much of each nutrient your fertilizer dose is adding and then you can use the calculator to determine how much potassium nitrate, potassium phosphate, potassium sulfate and magnesium sulfate to match what thrive was adding. you can get these items on the GLA and nilocg websites.
For CO2 I use an inverted bottle with no air in it. Once secured n the tank fill it with CO2. The CO2 will dissolve as needed into the water. Refill the bottle as needed. In my small tank the small bottle needs refilling about 4 times a day. So I use a timer to turn on My CO2 for only 1 minute 4 times a day. With an inverted bottle it is impossible to kill your fish with too much CO2. So you don't need a drop checker either.