Help! Please! Please! My Red Wag Platy is acting different! I just got him on the 23rd and now he is sick. Yesterday he wasn't using one of his fins and now he is just staying at the bottom of the tank. He is my smallest platy and the others picked on him a little but I'm not sure if they...

I am really worried about my Betta fish. I have had him for about 5 months. Just a while ago, I noticed a white dot under his mouth and a large white blotch on the base of his dorsal fin. I have pictures to to show it. It is on both sides of him! 'Ol Blue (his name) isn't really photogenic...