Got a def. starting, cant quite decypher it...

just started this morning, or so I noticed, and only on one plant.
DIFFERENT LIGHTING SO YOU CAN SEE BETTER:

been feeding fox farm trio with superthrive and mollases.
I just introduced a small micronutrient into feeding the last time I fed, all other plants seemed to like it and are fine...

second picture looks a little purple, like the start of a (P) def. Possible -IMO
Make sure your other things are in range water pH, roots, water. grow room temp, soil temp, soil pH.

Can you give a little more info about the soil? Did you add anything to it? Type of water used?

It's near impossible to be deficient in phosphorus with most mj nuts. You almost certainly are deficient in magnesium - while I can't see a stem they appear purple which is typically magnesium def. Diagnosis of these things can be tricky without extensive details.