Do you feed the fish daily? Just curious because the food should have been swirling around on account of the Lily pipes you have in there. I imagine it would be hard to miss that.
As a general rule, more light, then more CO2 and fertilizers are needed. Not sure where you got the advice on not providing fertilizers (I believe it was even mentioned in the other thread).
I think you would get better responses if you were to post the tank specifics such as: tank size, temp, filter make and model, light fixture make and model, number of hours it is on per day, type of substrate, CO2 and fertilizer routine (what, how much, when), any recent changes to any of the regular routines. Other helpful parameters, if you have them, such as ammonia, nitrite, nitrate, and phosphate.