First time grower having First Problem. WTF is thi...

could you take a picture or video of the underside of the leaves? Its hard to tell whats going on. The first picture appears to be a kind of infection or mold. The tip of the other picture looks like a burn from nutrients or lights or a combination of the two. If you look closely in the first two pictures. you can see other white formations starting on the leaves. could be water stains but that also means youre not using RO or Distilled water. Just beware of mold and burns. Keep the light at a good distance and dont keep things so moist. Also use clean water and benefical microbes. check your ph religiously and also your ppm. good luck 🙏

Hey, sorry for the delay in response. How are things looking now? Looks like your fellow growers did a pretty good assessment!

If this is in coco I would add some Cal/mag into your nutrient regime your leaves look a bit blotchy. The discoloration on the leave could be some nutrients or water was sitting on the leaves when the light was on which burned the leaf slightly. Speaking of your light a 600 watt light at 18 inches above a seedling is too close it could cause leaf burn and stunt your seedling/plants. I would use the maximum height recommended by the light manufacturer then lower it a few inches at a time. If the plant starts stretching toward the light drop it more. This could be lending to the issue. I hope this helps.👍

It is a burnt ! Could be due to a too hot temperature which is not your case so maybe you did spray something on the plant while the light was on and the water did make a loupe effect and burn the plant. Could also be a Ph fluctuation if your medium is coco because it can happens when you don't check the input and output values regularly