This isn't my betta but my grandmother's. I bought it for her a couple months ago and a couple weeks ago I noticed both of it's eyes are sort of pushed out of its head it looks like. I think the disease is called pop-eye? The crown tail is in a five gallon tank by itself with a heater and filter and underground filter. I clean the tank and take care of it all she does is feed the fish. So can you help tell my why this has happened? Thank you for any advice.