I don't think it would hurt to use it after it was washed off.
But some of my hardest learn lessons in life came from conversions and conclusions just like this thread. I can only give my opinion which really means little in your case, because I know nothing about shrimp. It is ultimately your choice. I just can't see where it would hurt to wash it off and use it again. I just wouldn't use the Miraclegro plant food as my substrate.