What's wrong with my clones?

My first clones. Any idea what I am doing wrong?

Have you fed them lately?

Yes I feed them every other day. LED lights about 18" away.

I think it might be nute burn or possibly ph fluctuations.

https://www.google.com/amp/s/www.ilovegrowingmarijuana.com/nutrient-burn-in-marijuana-plants/amp/