Light Burn?

This is one of two white widow autos, week 9.5. They were on 20/4 but I have switched to 18/6 since seeing this. Using a SF-1000. My Photone app was reading the correct PPFD but I’m starting to wonder now.

Looks like you might possibly have a herm.

I hope not but my concern is with the brown and yellow spots and discoloration on some upper leaves and very few lower/middle leaves

Dont think you'll be burning much with 100w spider farmer. Those free phone apps are not real reliable either. Even with a 'paper filter'.

Definitely looks like light burn.

Is it at 100%? If so, scale back to about 70% and let the plants adjust to the light before increasing the intensity.

Is the damage on the shoots closest to the led?
If the answer yes its light burn if not its something else.

It’s pretty much isolated to the top leaves, thanks.