Some Leaf discoloration has me freaked! Insights please?

Okc strain. Ffof 3.6gal air pots RO water,
going on 4 weeks old 18/6 cycle
480watt QB @65% day temps 70-78 40-50 rh / night temps 64-66 55-62rh
Topped last Sunday
inspected for pests and none, they were drooping a bit as they were due for h2o this am.
8 'think' the new growth looks ok
Any guesses? has

No added nutes other than roots excelurator and algen extract added to h20

You’ve given plenty of nitrogen. Note the deep green. They’re short and bushy. Try raising the light a bit and just water the next time. Are you adjusting pH on water and feeds?

I am not, total noob but I had read I didn't need to if I was using RO and no nutes?
Is this wrong
Idk because this is my first grow, but I read a lot.
Will take the light up a few inches asap
Thanks for the reply