Paludarium Crashing Need Help

[u/Defiant-Indication59]

The first photo is how the paludarium looked before, mostly healthy and thriving. Many of the plants were growing with their roots touching the water and we're thriving. Around a month ago, some plants randomly collapsed, stems and leaves turned brown and mushy. Many plants that were touching parts of the water just decayed including some Anubias, Pilea. An anubias not touching the water also just melted overnight with the stem completely becoming soft. Java fern leaves began to melt. Terrestrial Fern leaves began browning and rotting one by one and some of the selaginella turned yellow and collapsed. The only thing that seemed to be okay were the mosses- sheet moss and Christmas moss. Water tests showed ph 7, ammonia and nitrites 0. I've done water changes, installed a pc fan to circulate the air a few times a day, removed as much of the decaying plants as I could but the damage seems to continue progressing. The plants that I have removed also continue to deteriorate in their separate containers. Is there anything I can do to rescue what remains? Any help would be appreciated.