My Betta fish used to be all black with a yellow tail. Awhile ago he started getting these yellow patches on his skin that spread over time. Now he has not eaten and is just sitting at the bottom of his tank. I have gotten medicine for a bacterial infection but I am not sure what exactly it is. Do I need fungal medicine? I want to know what it is exactly so I can get the correct medicine. He has a 5 gallon tank but is not swimming at all now like he used to. He just hides in the hideout and never comes out