New Discus on his side...?

I have a very established 90 gallon tank- 8 days ago I added 2 three inch discus to my tank and they are doing excellent- my water conditions are identical to the tanke they came from. So I ordered another from the same store/company and picked up the fish still in the bag off the delivery truck so he wouldn't have to be acclimated twice and I got him about 24 hours ago now. he was stressed at first which I expected but after a couple hours his color came in beautifully and he was swimming with the other 2 discus. last night he was in a corner on the bottom stressed out again. this morning he looks even worse- on the bottom of the tank leaning against a plant. I know discus stress easily and I got him irght off the truck and that includes risks- but what should I do to help him? I have congo's and many other various tetras plus the other 2 discus.... If I can help him- I want to help! Please, any advice would be greatly appreciated!