First grow (Northern Lights Auto)

Looks like thrip damage but I doubt that's the case unless you have a much larger plant somewhere nearby. It could be the plant telling you that she's ready for nutes if you haven't given her any yet. Could be light problems especially if you're letting your leaves get wet or are misting. Try to avoid this. Remember that your plant only needs around 400 ppfd at this point (that's the amount of photosynthetic light). Your Niello light has 320 ppfd at 24" in the center. If your plant is directly under the center of the light, then I would say 22" or so is perfect. If you have 2-4 plants under the light, then 16"-18" is ideal by my estimate. I wouldn't worry, first true leaves often die off and they are really unimportant. If it speads to the newer leaves, then consider worrying... Good luck!!