NEED HELP ASAP

what is this? its only on one strain and only on about 4 leaves on the entire plant.

I'm almost certain it's calcium or magnesium because it's not ph

well first off u have a lack in NPK u have red vein that is a sign one of the 3 are off the plant needs more

2nd thing your brown dots could be the start of calcium def

Perhaps it's splash burn.
That leaf is very dark though. Too much N?
Would monitor closely but not act unless trouble gets worse.

Yes I doubled the nutes on accident one feeding during veg. So it's for sure nitrogen toxic just a little (no claw) and I'm using ro water so I'm almost certain it's calcium because it's not ph and I haven't gotten nutes on the plants