molly platy death help

Hi all i recently just got my first tank in September. I had comets in it for the longest time. About a month ago I added 6 mollies And 3 corys. on the 26th I removed the comets (as they were too large) and I’ve had 2 mollies die on me! I also added some more water as the water was getting low...

I have a 2 feet freshwater tank. I started with the following fish: 6 guppies 4 black mollies 4 platys 2 rainbow sharks 1 betta fish 2 zebra fish 1 white molly 1 spotted molly 2 orange mollies 2 white fish that i do not know the name of 2 orange fish (similar to platys) almost every day a...

Beginner here... I have a 15 gallon freshwater tank with : Current tank: 2 small glofish 2 bleeding heart tetras 2 white skirt tetras 2 long finned serpaes 1 sunsest platy 1 lyretail molly 1 small catfish (Deceased: 1 dalmation molly, 1 balloon molly, 1 platy Temperature: usually 84-86... but...