Not sure really as I had the same thing goig on two Weeks ago on some sour diesel plants and also the mother which they came from.... I just flushed them a little and turned the heat up a little bit on the mother room to like 76.. It went away for the most part so I just chalked it up to transplant shock and cold? Now the flowering plants look great and I just took a pile of cuttings off the mom?? Fingers are crossed?
Possibly too wet and/or too cold ??? Are the leaves brittle as well? Other than that I'm not sure. Good luck