slow growth

Hi, I've been trying to grow plants in my 20-gallon tank (no fish) for a couple of months now and I haven't really succeeded. I would very much like some assistance if that's possible? I've put a thick layer of Flourite Red as my nutrient gravel as well as having inserted a couple of root tabs...

I've just set up a 50L high-tech planted nano tank about 3 weeks ago.   I won't bore you with the details of how this happened, but basically, I have a mixture of ADA Amazonia and Eco complete. If I had to guess I'd say it's roughly 40% ADA and 60% Eco.   The substrate, along with the filter...