I'm trying to figure out a problem and was wondering if anyone can help me with this. I have been piping a topping on my cp soaps, but 5 out of 7 batches have gone rancid. The topping smells off yet the base soap is fine. Using the same oils that are in the base, so why does the top go off and not the bottom? Does it have to do with waiting for the soap to get thick enough to pipe? Any help is greatly appreciated! Thank you!!