Possible White Spot

Whitespot looks as though the fish has been sprinkled with salt. Spots we get as teenagers don't usually look like that, so your fish might have something else. I don't suppose you could manage a photo?

You do have to be careful treating a tank with shrimps or snails. It is next to impossible to catch all the shrimps and any treatment could seep into the decor and substrate. When I treated for camallanus worms last year it was months before my snails could go back (at least snails are easy to remove).
How many fish do you have in with the shrimps? If you do have to treat the tank it might be easier to move the fish and wait till any fish bug has died off in the shrimp tank before returning them. For example, whitespot will die without fish to infect so it should be safe to return the fish after a few weeks - though I don't know how many as I'm not sure how long it would take for all the whitespot parasites to die off.