standard Nute. burn
did you flush going from veg to bud
some shit soils demand it due to their high moss/vermiculite content
or maybe you just gave them too much food?
either way.. either miss a few feeds or pour 3 times the pot volume of air temp ph'ed water
allow to drain in a dim lit place or overnite
to continue in the morning
and then feed 50% less until harvest
good luck