Help, I've been lurking on this forum and multiple others for a similar answer to this.

There's this weird stuff that's been growing all over my java moss, driftwood and anacharis.

The blackout method seemed to have killed it, not sure, but it came back immediately a day later and started spreading like crazy.

Anyone knows what this is?
What should I do?
Is it harmful to my betta, snail and shrimps?
I've tried daily water changes, manual removal, lowering light amount, but nothing seems to help.

5 gallon tank
GEX slim S with seachem matrix filter media
3 Amano Shrimps
2 Cherry Shrimps
1 Horned Nerite
1 Betta
Plants: Java Moss, Marimo Balls, Anacharis, Java fern

https://imgur.com/a/OQuRe8Z
https://imgur.com/a/FpQAPvw
https://imgur.com/a/Z2xomsC