I’m not sure what you mean by seed booster.. but either way it does not look good to me. Looks like some bad growth of some sort to me.
I recommend using something different than those seed starters you have.. I’ve seen more problems from them than any other way to start seeds. I believe they hold too much moisture and can cause dampening off among other issues..
I use rockwool to start seeds, root riot is a great alternative too. Or just go straight to your final medium.