Some of the tips of my plants leaves are a lighter...

If you are going to use soil less media, you can't go guessing how much to feed; get a PPM/EC meter or you are going to have problem all the time, even a cheap one will do. In coco you should be feeding with every watering, but the correct amount

Ive had burnt looking tips due to 2 reasons..1. My lights being to close, hot, or strong. 2. Nutrient overdose. I think pulling your lights was a good idea, and like the others mentioned keep an eye on nutrients. I see you're doing fast strain and those typically need at least half strength nutrients...at least in the beginning. Oh also potassium deficiency can cause tips to yellow..unlike nitrogen or other deficiency which doesn't typically start at the tips. Best of luck, it's great seeing all these fast strains in action.

I don’t see it in any of the pics, but burnt tips is typically an indication of nutrient burn. You might want to consider backing down a little on your nutrient levels.