Hmm, is the fluorite a month old or the substrate itself?
Most plants tend to feed from the roots more than free floating nutrients.
If the substrate doesn't have alot of crud in it they might not be getting enough to feed off of.
Pick up some flourish tabs. I put atleast one at the base of the bigger plants and go a little over the top in the rest of the tank (not much, but they're closer than the box says to do.)
A ritch substrate is a major part in good plant growth, it also doesn't contribute to algae growth as much as water born nutrients, dry ferts are only a small part.