Hey Growmie ...
This is more than likely being caused by overfeeding so a good flush would certainly help. With autoflowers they only need about 1/4 the dose that companies recommend because the feeding schedules are based on photoperiod plants and what they can intake, using their schedule will almost certainly burn your autoflowers every time.
Hopefully, this was helpful and remember ..."Happy Growing" and "Free your mind one puff at a time".
Mr_Weeds_Autos.