About the end of week 4 the buds can start getting thick traping moisture inside.
By the time you will notice is week 6 and its to late.
The only thing you can do is cut the bad bud out and hope air moves better around the others...
An it dosent take rain to cause mold or bud rot a good frost can, and high humidity can as well. So if gets fogging once the buds are getting close to ripe keep an eye on them...
Dice