I've gotten some of this lately and coincided with an unusually elevated VPD. It never progressed and stayed isolated to those leaves from that time frame. Can still see them at very bottom of my canopy, now.
did this damage occur in the past when those leaves were near the top? if so, it may have been too much light relative a blip in your climate control. How close a light can be is in part related to VPD. I can get my lights 12-14" away if my 'atmospheric-temperature-calculated' VPD is in a normal range (leaf temps are cooler than atmosphere, so i can't give an accurate value)
The leaf does look too lush. At the least, may want to draw back supplemented N in your fertilization formula. If the interveinal damage progresses, might be locking out (i.e. inhibiting with high concentrations of other ferts) some trace elements.