Agitated Betta Shredding Tail!

[Lebroo9350]

I have a young half moon betta. I have had him for about 3 weeks now. He is probably 6-8 months old. I have recently put him in 2 gallon aqurium because of his activity level and he seemed to respond well to it. Today after getting home from work, I stop to check on him and the other bettas I own (separate containers), and he has multiple holes in his anal fin and caudal fin as well as complete splits. He has lost multiple scales as well. He is highly agitated. I can not even walk past him with out him flaring at me as if we're another betta fish. He has always been docile with people especially me. What can I do? It has been a week since I changed his water and I know it is time but I am afraid to stress him out further with a water change. What could be causing his issues? He was axting absolutely normal this morning. I looked him over really well because his caudal fin looked off from the angle I saw him, but not wholes and complete splits. Please help me!

 

[snazy]

One week without water change? Is there a filter in this bowl as he is probably stressed from ammonia poisoning? I would do a water change right now with dechlorinated and temperature matched water