Nutrient Burn or Nutrient Deficiency?

strangely enough, it can be a tough call, especially in this soil - it's evil at times
my first grow was in MG Moisture Control, had a deal similar to yours
it's probably deficiency, i suspect it will progress
i moved away from the pre-fertlized soils, but from what i read, the MG time release soils can be very flakey with respect to the PH of the water, there's a zone that works well, and a zone that does bad things

nute burn from mg soil.
more you water the nutes it releases.

It could be neither. it is minor leaf damage that might be the result of a temp variance, humidity problems, insect nibbling, rough handling, or just plain normal brushing of leaves together in the breeze.

the leaves look like they are the right color, and the growth is full and lush. unless that plant is like 2 months old, or more, then youre doing just fine.

unless it gets worse of course, then is prolly nute burn.

deficiencies usually show up as spotty patches or discoloration, not leaf damage until it gets really bad and the plant is starving to death.

usually nute burn starts at the tips and moves down the leaves, just frying them. i say def or lock out.