Leaf turning brown

FIRST LET ME TELL U WHAT I GOT. I RUN A 4 BUCKET HYDRO SYSTEM WITH A 15GAL RESIVORE. THE WATER NEVER STOPS AND AIR STONES IN BUCKETS AND RES. 2 FANS ON LOW. 1 HUMIDIFER,44O CAL LED LIGHT IN A 8 FT. TALL,4X4 TENT. YEA THE BUCKETS AR 5GAL. WITH CLAY PEBLES. A PH OF 5.8 TO 6.2, AND TEMP OF 77 TO 81 OR 82. 55 TO 60% REL,HUMIDITY AND IN THERE 3RD WEEK OF GROTH WITH 750 PPM WHICH TO MY CHART IS IN THE MIDDLE OF PPM RANGE. PROBLEM, ONE PLANT LOOKS LIKE IT IS BURNED BY TO MUCH LIGHT BUT IT IS 18IN. ABOVE TOP OF PLANT. IT ALSO LOOKS LIKE IT GOT TO MUCH NITROGEN ON IT BUT I DONT C HOW BECAUSE ALL 4 PLANTS GET THE SAME THING. WHAT AM I MISSING. IT IS RUST OR BURNED OR SOMETHING.BUT THE TOP IS CLEAN AND IT MIGHT GROW OUT OF IT. IF U CAN TELL ME WHAT U THINK IT WOULD HELP ME ALOT. THANKS TO ANYBODY THAT CAN HELP ME.

What do the roots look like on the one that has burnt leaves?

THE ROOTS GO ALL THE WAY DOWN TO THE BOTTOM OF THE BUCKET JUST TUCHING AND ARE WHITE AS SNOW. THE LITTLE SHOOTS THAT COME OFF THE MAIN ROOT ARE ALSO WHITE. THEY ARE ALL NEW ROOTS 3 WEEKS OLD. ALSO NO BAD SMELL. I HAVE READ ABOUT ROOT ROT AND I AM SURE IT ISNOT THAT. DONT GIVE UP ON ME PLEASE.
SAM SMITH

Are they different strains?

WHITE WIDOW ALL THE WAY AROUND. 4 OF THEM. BUT I HAVE NOTICED THAT IT IS GETTING BETTER BUT STILL THERE.

Piks would be nice. LED lamps can burn the crap out of plants from what I have read. MacG; You should chime in on the light distance.

Everything you are doing seems spot on. However; I do not condone running nutrients wehen the lights are out. NO need. No Light-Plant does not feed. Lights ON! PLants feed. Peace

I’m not sure what type of LED he is saying he is using, but in most instances 18 inches away should be plenty, I don’t think that is the problem. Maybe something created a hot spot on that side of the canopy? Maybe the way air circulated? I’m at a loss.

Only other thing I can think of is – if it is the first bucket inline in this 4 bucket w/15 gal reservoir? If it is the first inline from the reservoir, because if you mixed your nutes in the 15 gal res. that first plant might have received a stronger dose until the nutes had time to mix with the entire water volume of the entire system, just a thought…