I don't have a ton to add, but as a fairly new person to the hobby I can empathize with your situation. I experienced something similar.
I did all my research, bought all the "right" stuff, planted my beautiful new plants and then watched in horror as they melted and browned like crazy. Cue distress, internet research, water testing etc. My local fish store encouraged me to stop fiddling with the tank and give them time. Lo and behold, after a few weeks new growth popped up. My water sprite, which melted down to nothing, is growing out of control. I find it's difficult to step back and let nature do its thing, but that's been the best advice I've gotten.
