Beta fish becoming anti social
Hey experts I'm new in desperate need for advice for my male beta fish. I've had him for about two years now, and he has always been happy making lavish bubble nests and excitedly interacting with motion and my voice. Recently he has become very reserved and spends most of his time inside a moon rock hiding. However I have caught him several times, late at night or when no one is around, hanging out near the top nestled in bamboo roots. Then when I try to feed or talk to him he consistently rushes down into his rock. I don't think he's eaten in awhile. I use distilled water, which I have always used. I tried the water stabilizer once but stopped when I realized he appeared miserable. I think the temperature is okay because I currently have another beta in a bowl on the table set apart from him who exhibits normal happy beta behaviors. Sad and distraught for my old pal. Any advice?