Discoloration on new growth

I have one leaf of new growth that appears to have a bit if browning along part of the edge. What could this be?

Shes three weeks old. Medium is FFOF. My RH has been around 50%, temp 78F-84F. Did one gallon so far today: Calmag at 33% strength, solution PH 6.6, runoff PH 6.2. Two days ago I did 2 gallons, one a.m. one p.m., using FF big bloom at 33%, solution PH 6.7, runoff 6.3. The medium has been drying well.

Using 900w LED at 17" from top of plant. Just dropped it down today; was at 30". This started showing prior to dropping the light though.

Take a pict without the purple light and we could see it better. Thanks

Sorry about that. Here’s a couple new pictures.

Plant looks fine: STOP feeding it!

One gallon and two gallons of what?
If your watering that much with a plant that small it’s way way way too much unless it’s in like a 50 gallon pot and even then not enough plant to use that much hydration let alone if your adding nutrients to that.