Need advice!

I've been out for a few hours so I don't know when this happened. Ive just come back home and thouht i saw a leaf on the floor, unpon closer inspe ut was one of my corys. I immediately picked him up and he moved so i put his straifgt back in the tank. At first he sunk to the bottom on his side and then readusted himself to where he has been sitting breathing heavy for the past 15 mins. For reference, I added this group of 6 Cory's a couple of days ago and have been getting on very well.

Is there anything I can do, or just wait and hope?? I've pulled up a chair to keep and eye but not sure if there is anything else I can do!