Now that you have the whiskers under control, it is time to work on the alloy and mold temp. You say that the mold is preheated but casts with wrinkles for several casts. That indicates the mold is not up to temp. If the mold is not filling out well, even with the whiskers, then you probably need more heat. While at it, you might as well weigh some small ones and some full sized ones, just to see what you are making. I am suspecting rounded edges or bases but no photos to show what you have. Do you pour a generous sprue or just a little button? How long does it take to freeze over?
Dusty