4 days ago i noticed my betta acting strange, he didn't seem as active as he usually is and he was ignoring me which is highly unusual. Seemingly over night he developed a thick white fluffy cluster on the end of his tail fin, he also appeared to be very bloated. I treated him for 3 days using Esha 2000 and 4tsp of aquarium salt with 20-30% daily water changes. I also removed the gravel as i've been having issues with cleaning it anyway and saw this as an opportunity to get rid, i have used sand from my 15 gallon aquarium rather than using new sand so not to disturb the bacteria balance too much. Right now my betta is acting very lethargic, He is no longer bloated and does not have the growth on his fins now, however i have noticed when he comes up to catch some air he is franticly flicking through the water and brushing up against the heater. He only eats his 2 pellets in the morning, he doesnt come up for food after that as i usually do this 3 times a day. Is this just him recovering from whatever illness he had or is he still very sick? Does anyone know what this could be and how to treat it? It's quite upsetting to see him in such a way. Im attaching pictures of his before and after treatment just incase someone can diagnose if he has anything and what i can do. These pictures are over the course of 4 days. The pictures do not show him on the first day when he was bloated.