Hi- new user here. I am having issues recently adding new fish to my 29 gallon tank. Lately, whenever i add new fish, they devlop white spots on their mouth and their back fins turn white. Some have died after 2-3 hours of adding to tank. Other fish already in there seem fine. I did test the water and had 0.25 ammonia but have been treating with prime and stability which should neutralize any ammonia. What could issue be? Should i treat tank for fungus? Thanks.