Hi! I have 12 platy fry in a 5 gallon tank. 5 are a few weeks old, 7 are only a week or two old. One of the 7‘s tail fin is jagged and white on the ends. The water was dirty because I waited for the newborns to get a bit bigger before doing a water change. The tank is also infested with ramshorn snails, but I will get rid of them once I get the fish out of the tank. I removed the sick fry and did a large water change. All of the other fry look healthy. Is there anything that I can do for the sick fry? Also, is aquarium salt safe to put in the 5 gallon?