3yr old goldfish in 75 gal with two 8 mo old goldfish. His top fin had a small tear a few weeks ago. I purchased the Fritz paraclease and maracyn. I treated the entire tank with the 2 plus inch-x 5 days ago. I noticed some of his larger tail fins are splitting now. Not as bad as the top fins. The 2 younger fish look healthy. One has a minor spilt. The 3 yr old is active when I’m around but mostly rests in the corner. The 2 younger are active but will cuddle with the 3yr at times. I have two 75 gal hob and two sponge filters. I do a 50% water change weekly. I’ve treated the tank on and off with prazipro because one of the younger ones came with worms and I’m not sure if they’re completely gone. Ammonia 0, nitrite 0, nitrate 5, ph 7.6, gh 12 drops, kh 6 drops. Im emotionally taxed. Id appreciate any thoughts or advice.