CO2 is clearly the biggest problem. For a tank that size I would expect to see about twice that much bubble rate, and the small pH drop also indicates too little CO2. Rather than use the pH controller, which is really doing nothing of value for you right now, I suggest just leaving it off, and controlling the bubble rate to get the rate that maintains the CO2 concentration in the right ballpark. A drop checker will help you to get the nerve to increase the bubble rate as far as it probably needs to be increased. From there you can very slowly increase it a bit every day, watching the fish for signs of distress - they would cluster at the surface like they are gasping for air if the CO2 level is too high. Also, you should get some easy to spot pearling before halfway through the lights-on time, if you have enough CO2. Once you get that zeroed in, and if you stilll want to use the pH controller for something, just set it to control the pH at the level it is when you have the CO2 bubble rate right. But, be aware that if the plants grow a lot, and build up much more plant mass, you will need an even higher bubble rate - probably a lower pH.
Seachem's fertilizers are essentially water, with tiny amounts of powdered fertilizer dissolved in it. It is expensive water. If you buy some powdered fertilizers, KNO3, KH2PO4, and CSM+B from one of the online stores, you will spend a lot less money, and get much the same fertilizers. But, if you want to continue with Seachem fertilizers, at least increase the dosages considerably from what they recommend, which is for a low light aquarium.