Hey guys, I came home today to find my flowerhorn had some kind of zit looking thing on his tail. He is very normal besides the zit. He is in a 55g tank with a frontosa and a pleco. Water temp is at 80 degrees, ph level at 7.8. Other fish are fine. I immediately did a 20% water change and added aquarium salt. The last water change was last week. Any suggestions would be appreciated. Thanks.