My black molly is gasping at the top of tank, clamping his fins, his tail is becoming discolored as well as silver spots around his gills and his poop is white and chalky. His poop has been like this since I got him so I assumed it was normal. His diet is flakes, freeze dried blood worms, frozen blood worms, and frozen brine shrimp. He also gasped at the top of the tank but never to the extent he is now and also is constantly breathing heavy while swimming around and doing weird yawn things. There is a bubble wall so I don't think its from lack of oxygen. I gave him a salt dip and did a 25% water change. I haven't tested the water yet because I just did the water change and I am not sure if the results would be accurate. Could this be an internal parasite? Please help!