I've recently been buying sliced sharp cheddar from the deli dept. (It's sliced from bulk) after 5 or 6 days I've notice what almost looks like "salt"? all over the slices. Is this truly salt or is it some type of mold growing on the cheese. I keep it in the refrigerator in a ziplock bag. I'm wondering if it is still safe to eat. Can somebody educate me please?