Okay, I use only Essential Oils, I have gotten a new bottle of peppermint oil, and a I've tried even various Patchouli Oils, chinese, indonesian, only to have the same results, early Dos. In the peppermint I use a powdered earth mined pigment, I went from 1/2 teaspoon, to barely a 1/16 tsp. of colorant. This past time I put on top peppermint tea, dried, just a sprinkling, and it seemed to get yellow around it first!! My other oils are fresh, I do use some soy, but thinking of ditching it. I use olive, palm, coconut. My supplier seems very reputable, only packing in the best aluminum, but lined bottles, very large company. I made batch before last that still hasn't dos, but this past batch did, very strange. I'm thinking could maybe I insulate those two types too hot, do they spoil easy. Does peppermint and patchouli easily rancid?
Sonia