They could have got a shock. My canister filters,and mind you I think I have one of each,lol, sometimes shock the water when I need to replace a seal or re-silicone the primer. My fish immediately race to the surface and stay there until I come fix it. If you had just cleaned it, you may have bumped a seal and it needed a chance to re-seat itself and so they stopped getting shocked and so resumed normal behaviour. That is just my guess if everything else was spot on.