If the plants are rotting at the stem-usually that can mean the soil went anaerobic or you didn't have proper lights/photoperiod.
What kind of soil, how deep, how deep on the sand cap, what species of plants, type of lights-kelvin, watts, age of bulb and photoperiod-Did you have any trumpet snails or did you poke the soil and if so-how often.
How long was the tank setup before the plant failure-did any plants grow-how many and what species of plants did you start with and what kind of water changes did you do. What kind of partition between the lights and plant...also tank size.....
miracle grow organic garden soil, about 2 inches, sand cap was less than an inch and now is around an inch, Plants are narrow leaf anacharis, Bacopa Carolina, Cryptocoryne retrospiralis, Foxtail "RED", Brazilian Pennywort, Rotala Rotundifolia (Indicia), Pigmy Chain Sword, Green Cabomba, Dwarf Lily, stargrass and some floating water sprite. 10 hour light period.
It's been up for about 2 weeks, they barely grew except for the dwarf lily kept on it's constant growth, did about 3 water changes, It's a normal florescent aquarium light system, light bulb was what came with it, trying to get daylight bulb. It's a 15 gallon aquarium.
Oh. and I'm most likely going to get MTS, since I don't over feed, they shouldn't over produce.