If you want better plant growth, then provide CO2.
That is the limiting issue.
240w on a 75 is a lot of light for a non CO2 approach.
Eco complete is NOT a substitute for CO2 and does not mean you do not have to add it.
Adding CO2 is something that cannot be done via the substrate in any appreicable manner like they suggest.
Adding CO2 will always help plant growth, no matter what type of substrate you have. Eco complete also expensive.
I have non CO2 tanks with flourite, peat and mulm.
Kitty litter works quite well, but the tank will cloud when you replant unless careful. But Flourite, eco complete etc are all iron rich clays.
I'd also get some algae eaters in there, SAE's, Amano shrimps etc.