Plants melting from base up?

First pic is from 4 days ago and last two are today. This is my first tank that I’ve had for roughly 6 months total (cycled for 2 months with plants before stocking but have had to continuously replant since then) It’s happened with four plant species total so far but i plant them, they do fine and even notice it start to spread already with beautiful roots all while the leaves at the base start falling off (not even melting, literally just detaches from the plant and floats away to make a mess) then when the bottom half of the plant is bald the stem starts to melt until it detaches like a clean cut and the whole top half ends up floating and staying healthy for the most part as seen in the last pics while the base continues to melt to death. Ive heard it’s normal for newly planted plants to melt a bit then bounce back but these guys don’t even get the chance, they literally detach themselves by the base of the stem within a week. It’s happened on two separate occasions with rotalia and now the second time with this bushier variety as well. I have vallisneria and two fern species that have been there since the start and will only melt one or two strands occasionally but the overall plant is healthy and abundant. When i plant them i put root tabs deep in the substrate where it’s planted but still no luck. I don’t know what could be the issue unless my light isn’t strong enough? I have floating plants but i weed most out twice a week as well as having 4 floating windows. Please help, I’m sick of buying plants just for them to fall apart and cause a mess by the next week! Tank is a 10 gal tall stocked with skrimp, (1)rabbit/bladder/ramshorn/malaysian trumpet snails, and 4 otocinclus. (there’s no betta i just like when any of my babies chill in the floating log)