I seriously DON'T have any rotting plants. All my plants are pretty hardy considering this is a low tech. Crypts, java fern, amazon swords, java moss, anubis, dwarf water lettuce floaters, and those plant bulbs that you buy from petsmart. Nothing is rotting. The only thing they have on them is brown algae.
I'm getting so many variety answers and i have no idea what to do. My LFS said it's because of my high phosphate (1.0 ppm) and they told me to try Phosguard. But someone on this post said 1.0 ppm is not considered high.
Your plant's WILL soon be rotting.
Once algae cover's the leaf /leaves of plant, the plant cannot take nutrient's (which you aren't using) across the leaf.
No fertz = bad new's for plant's.
According to other post's,,you have two 54 watt T5 bulb's.
I would raise the light,or shade the light with layer or two of window screen.This will reduce demand for CO2/fertz.
Would at very least,use some Flourish comprehensive as per direction's once or twice a week.
Or,purchase dry fertilizer's KNO3,KH2PO4,CSM+B and add 1/2 tsp of each once a week a day after water change.
I use same dose once a week in 80 gal low tech.
Keep filter's cleaned regularly(monthly).Clean glass weekly,rub off brown algae if you can from plant leaves.
My two cent's.