I just went in to feed my Bettas and I noticed my female, Amethyst, has a bulging, swollen eye right eye. Under and around where it's bulged it's pinkish-red partway up to her mouth. It's so swollen that it almost looks like the fins have a pinconing effect, but it's not all over her body, it's just centered on the swollen area.
I tried to get a picture of it but she's scared of my phone and I think it was beginning to stress her out because she started darting into her cave to hide.
I've attached two photos. It was the only photo I got of her (I tried to cut it down and sharpen it in photoshop, but it didn't work very well because it was so blurry - caught mid-swim - to begin with) before she started really getting upset. But you can kind of
see what I'm talking about with the swollen eye and pinkness even with the blurry picture.
As soon as I saw her I used my 5-N-1 Test Strips to check the water levels, but the nitrate and nitrite were both in coming up in the safe range and the total alkalinity was showing up in the ideal range.