Please help! We got a veiltail beta about a month ago. He has always been active and playful and 4 days ago, I did a 25% wc and noticed over the last 2 days he was no longer active, hanging out near top of water, not eating, bubbles coming out of his gills and then he died this morning. I always test the water (API freshwater master test kit) and numbers appeared good so I'm baffled. Taking a close look at him with a magnifying glass before he died, appears to be ammonia burn? I have included a few photos of Iris (yes a girl's name - my daughter's fish ;-) early on when we got him and recently of when he started getting sick. Any thoughts or confirmations that this is indeed ammonia burn? Tank info: 5 gallon, filter, heater (set at 76 degrees), 25% wc every week and 100% 1x month, feed frozen live food.