There are some people who import WC fish so may have a better idea. Firsi thing is to make sure the water is clean and the light is dim. You may then want to start a cycle of medication to clear them of parasites. But clean water is an absolute must, I'm sure there are others who can give you recommendations on the medicines. But be patient those fish are pretty stressed after their trip from the lake and are not used to living in a glass box.