i was going to say possibly undiagnosed root rot, finally made its way up the plant?? but lurk seems to have a better idea, with more actual "facts" to back it up, haha. good luck!
After looking back on my grows I have discovered 2-3 things that caused major problems.
Root rot happens sometimes, but you can easily trim off the rotted roomass and move on. Buddy of mine had a blueberry plant going downhill, we trimmed the poopy rotted roots off and she has looked like a champ ever since she recovered from the root trim.
Shit really hits the fan when you have root rot and then pH issues.
They are fixable on their own but not together. (At least from my experience)
Root rot causes your plants to be extremely droopy and saggy, when your older leaves and nodes start going limp root rot has taken over.
Almost ALL deficiencies are caused by pH problems, which create salt buildups and issues with plant nutrient uptake etc.
I really hammered my pH and shit first few grows but I got lazy and stopped monitoring it so much and it fucked me hard in the end.
Just because you are running the same strain doesn't mean every plant will react the same to envinronmental changes at the same rate.
3/4 plants might look good now and then further down the road they croak for the same reason the first one did, they didn't show the symptoms but they all had it.
Hell yea alex!!!!!!! THOSE ARE SUM PRETTY BUDS MAN KEEP UP THE GOOD WORK
