My 11 year old fish is laying on his side at the bottom of the tank alive why?

My male gold fish I've had for 11 years is laying on his side at the bottom of the tank but he's still alive his mate is doing the same and she's only 3 years old? I have two other fish in the tank a tiny black moor and a sucker fish and they are perfectly fine. They started falling over like that after I added an air bubbler. When I noticed them doing it I took it out of the tank. But for some reason they're still on their sides at the bottom of the tank.

They could have an air bubble in their stomache! Really easy to fix, just boil them some peas! Goldfish and bubbles don't mix, they like to eat the air and it makes them fall over on their side, and they look disoriented! Feed them pea skin until they swim normally again🐟