I agree with Dreamerr about mold often causing problems. For sure you don't have to see it for it to cause problems. Maybe it was grown outdoor and there was a lot of rain near harvest and it got contaminated, maybe it was grown in an apartment with mold problems, or basement. Maybe it was not dried properly and got a chance to get mold growth..many reasons! I have become sensitive to mold and it is a big problem to have good quality mj without any mold contamination. please people be careful with mold as strong exposure to it might change your life as there is no way escaping it so much better to avoid in the first place than become highly sensitive to it.