Yes, you are likely correct, it is also apparent that you are aware of the situation.
I started to answer a couple of times but it is difficult when so little information is given.
I, and I am sure others would be happy to try to help. Perhaps you could provide further details about your tank,lighting, filtration, CO2 if you are using it, is it a pressurized or do-it-yourself. dosing routines, aims (goals) and generally how you arrived at your unhappy situation.
As I said it is likely that you are correct, that CO2 is the problem, at the same time, based on the information given, I don't even know if you are using CO2 and if you are, how.
If you can provide more information, if I can help, I would be happy to help.
I just did a search of your other posts and I think I have a better idea. But threads kind of stand on there own.
By the way, now I really do believe it is primarily a CO2 issue, though I suspect other issues as well.