Nute burn? Or light burn?

Not sure if this is nute burn or maybe light burn. It's only showing on the very tips of leaves on the canopy level mostly. Day 25 into flower at 12/12, it started showing up 10 days ago with my last rez change with technaflora nutes at 2/3 strength of their chart for flower. Ppm at 1050 with tap water at 50 ppm. So I fed it just tap water ph 5.8 over the next week to keep it topped off and lower the ppm down to 770 over that week.
Changed rez two days ago and went with 1/2 strength this time, ppm 850 @ ph 5.9, it seems to still be burning the tips a little still, with a few brown spots on fan leaves, seems like nute burn to me? Maybe this amnesiac strain is a light feeder?
Also, they are under a Kind 600 led at 15 inches above canopy, and as high as the light can go and it appears the stretch is pretty much over I hope. Lol
Newbie here on his first grow, any help would be appreciated. By the way, this is a 2 plant grow in a 3x2x6 cabinet with RDWC.

Sorry for all the questions, should I cut some of them fan leaves on the canopy to better expose some of the bud sites to light, or would that be more harmful to the plant at 3 1/2 weeks into flower.

Honestly they look great! lol. Those little yellow tips can happen for a few reasons, namely an excess of potassium or phosphorus, a zinc deficiency, or, either a toxicity or deficiency of sulfur (both can lead to burnt tips). Keep an eye on them see how they change.

Chumly said:

Sorry for all the questions, should I cut some of them fan leaves on the canopy to better expose some of the bud sites to light, or would that be more harmful to the plant at 3 1/2 weeks into flower.

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I tend to remove interior fan leaves only if they seriously block bud sites from light. As the colas develop, I also defoliate a bit more aggressively.