I got this blue Atlantic tang 5-6 days ago in my tank and it’s been doing great so far. I woke up this morning and see that it’s just laying in the tank on its side. The color appears to be good on the fish and he does move sometimes if I get close to it. He does sometimes swim around for a bit and then goes to the top of the tank and bops up which and down which I haven’t seen it do but then continues to lay down. I am very worried. What should I do?