What kind of scopes are they? Are they inexpensive or very old? If so the seals could have failed and it could be moisture has gotten inside and you are seeing condensation droplets or mildew possibly. Seems odd that it would happen to multiple scopes though. Tell us more about how they are stored and used. Is it hot and humid where you are? are they left in the sun? Do you keep the lens caps on when stored? Is it possible that something splashed on the lens that dried and left spots or damaged the lens coatings? Some harsh chemicals maybe?