Could it be bloom nutes too early?
Looks like you could have used more “N” early in flower.
No sense in adding it now, just in case you are thinking maybe???
Check your run off/out to see if it is high in ferts aka EC.
Possibly too much "K’ built up in the soil, if you reuse your soil or feed too much VIA boosters.
This could happen if you were feeding straight water instead of food too.
Underfed, or improperly fed is my guess.
Unless you kept them totally soaked all the time, that may just do it too.
Not a bunch you can do now just ride it out till the end.
Good luck
Shag