So I'll start off with the basics: water parameters are ammonia: 0, nitrite: 0, nitrates: 20, pH: 7.6, high range pH: 7.4. It's 45 gallons, and I keep it around 75 degrees, it cools off a little, maybe down to 70 at night, and on hot days it can get up to almost 80. I do a weekly 10% water exchange and the fish seemed happy and healthy. There are 4 platies, and 4 mollies as it finally balanced out not long ago and I'm working on getting it where I want it to be.
Saturday I noticed my Dalmatian molly's top and bottom fins were clamped. She was swimming normally, eating normally, but has clamped fins. Then she started getting more aggressive towards the silver lyre-tail. Chasing her around for apparently no reason especially at meal times, or when she just gets too close. I thought I had seen her "flash" against the heater, but it could have been a result of trying to chase the lyre-tail like she has been.
Then today I noticed one of my platies rubbing herself against one of the marbles in the bottom of the tank, and her gills look red and a little inflamed. Her fins are not clamped, she's eating normally, swimming normally and she isn't aggressive at all to any of the other fish. Her body is getting bigger but I'm assuming she's pregnant as I recently purchased her from the pet store and there's always a greater chance the platy will be pregnant than not, but now I'm not so sure.
The weird behavior with the molly started shortly after I started feeding them the Jungle Anti-Parasitic fish food that I always use whenever I get new fish as a precaution. I do not have a quarantine tank, nor do I have the funds to get one so I try to take every precaution available. I thought she was just unhappy with the change of diet and that after the three day period of the medicated food she would calm down. It's day three, I've already fed them the medicine, and the behavior is getting much worse.
I also, literally, just noticed my Sunburst platy acting strangely. She's hovering in one spot, her fins clamped and she's swaying her body back and forth very strangely but not really going anywhere. Then she'll swim around for a few seconds, and repeat the behavior. All of these behaviors have popped up over night and I have no idea what to do. Any advice would be helpful and greatly appreciated. Thank you for your time.