Here's a little update.
So since the start of my planting I've closed the two air holes and have kept it sealed. Everyday I let it air out each day for about 15 minutes. Every morning I've been spot treating with a 1:3 H2O2 solution with a dropper and mist every other day with water/excel and it seems like it's doing the trick. I've noticed less fungus/mold each day.
On the bright side, everything is healthy and it looks like my HC is growing new roots! (sorry for the picture, wish I had a macro lens to shoot with)