Corry Fin Growth. Trying to find cure.

Hey guys. Creeping on this reddit for some time and have had a lot of success from following past posts. I have a 30 gallon tank, understocked at about 16 inches of fish. Two balloon mollies, three normal mollies, a platty, a dwarf gourami, and three green corries. I have two established mechanical filters, one for a 20 gallon and one for a 50, (I run the small one at night to decrease noise but keep up filtration.) In addition I have an aquaponics grow bed on top currently growing bok choy (this is an old photo, currently the bok choy is big enough to harvest) ph is high sevens, water is pretty hard, visability is crystal clear, low amonia, nitrites and nitrates due to plants, I will actually have to add more fish soon if I want to grow the plants any bigger. So my question, look at the pics and tell me what you think. The small growth on their top fin appeared a few days ago on one, then the other, but not on the third yet. It doesn't seem to bother them, no changes in daily behavior. Tank is currently at the tail end of an ich treatment woth kordons 100% natural ich attack. Look at the link, and give any and all advise. Thanks

https://imgur.com/a/2Vxsw