You're koi need time to adjust. Just throw in the pellets, and walk away. If they can't see you, they will eventually learn to come up and eat the pellets.
I raise koi, and the ABSOLUTE MUST when getting new fish is Quarantine for at minimum 2 months. For Koi that is... Koi carry KHV (koi herpes virus) which is a fatal disease that kills EVERYTHING and you have to start over.. even buying new filters and liners. When exposed to stress, the signs of KHV will come out.
If you got them at a petstore, they more than likely have parasites, and if they are outside, and warm, then the faster the parasites will spread and then your whole pond is infected. The best thing for koi when you get them is to QT them with a salted water of .3%. It will kill the parasites.
If you get snow, or the water gets cold and freezes over winter, you will need to bring them inside. 2.5 feet is not near deep enough to keep them from becoming Koi Pops.
They are just stressed, and they should be fine in a week though.