Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Do you have any way of measuring the CO2? If not, I would get a drop checker. They are cheap, and I have heard some questions about accuracy, but I think if you get one you will have a better idea about what the CO2 is doing. Then you can adjust it to provide the maximum possible, and make sure it is getting properly dissolved and distributed to the plants.
Once you get the CO2 on track, add more fertilizers. I would add significantly more of everything, making sure you have plenty of N, P, K and micros. Look into the EI method as a start. Once you get the fertilizers lined up you can start to back off, but do not reduce the dosing too far.