I have sprayed the coop with Virkon sold to me by a vet. I noticed after we fogged that the package expiration date was just passed. We are hoping this will not affect the potency of the product a lot. However,I am concerned that this product will not rid the coop of the original problem--lice/mites. I thot I read in a past post what to spray but,darned if I can find it! Can anyone advise?