buds changing density week 6?

So on my outdoor grow, not sure of strain but I'm guessing from stature and leaf size , definately a sativa/indica hybrid. Anyways, about 6 weeks into flowering the kolas will get hard and dense to the touch but still have all white pistols and clear trichomes, I have one plant that is farther along and just like past yr around week 7 the bud seems to shrink and not be as dense as it was before, but now is starting to ripen. What could cause this? Is it normal? Happened last yr as well. could it be the strain? Any info is appreciated. Thanks in advance

Nobody else has had this happen? I've had it two yrs in a row lol maybe strain related I guess

Ripen ? Is it cold out there ? A plant in flowering time isn't too hard to follow but if you forget about it you may fuck it up !! I think it's cold !! Are you giving some stuff like NPK 5-15-15 ?
Switch to 15-30-30 and stop 2 weeks before harvesting !
or switch again to the 5-15-15 for one more week and stop a week before harvesting !! Cheers !

Yup its cold for sure already went through a frostnd daily highs are only around 7 or 8 . I have flushed already and they r packin on the crystal but still don't seem as dense as they were a week or two ago.