WTF is this?

[Gorg]

I am growing 3 Jack Herer autos, and 1 phenotype grew out twice as tall as the others and is unfortunately only a few inches from my 600w LED because I can't raise my grow light any higher in my 180cm tall tent. I am in week #12, and everything has been fine concerning the distance from my light, as it has stopped growing in height for the last few weeks and has generally been around the same distance. However, just tonight I looked inside to check, and only a few of the leaves on the top of the main cola started to turn orange on the outer points of the leaves (left and right, not just the end of the leaf), and there are these orange-like spots over them that basically look like random tea stains. I was thinking initially that there was some sort of nute deficiency going on, or maybe some sort of odd pest...but it's ONLY on the top few leaves on the main cola and on 1 plant. Is this light burn, or what? The outer tips aren't significantly curling and there is no taco-ing. Does anybody have any idea what this could be and how to take care of it?

 

[SmokingWings]

I had a clone grow up to the LED light and then the tip turned off to the side and up and around the fixture. The leaves above the fixture did nothing out of the ordinary. The leaves that touched the LED tubes looked normal for a week or 10 days before they started to turn colors and then turn yellow. Never saw any canoe or taco shape develop.

The lights were T5 HO fixtures with the LED tubes instead of the fluorescent bulbs. Gotta keep in mind that my lights were not as strong as your light fixture. But, before the strong yellow color showed up the leaves did slowly turn color similar to what yours are doing.

Never did worry about it. After awhile I just cut that shoot off and stuck it into a small pot to see if it would root. Cutting it off just made the plant a more uniform height for when I put it into the flowering cabinent which only has a touch over 4 feet height for floor to lights.

IOW, I don't know what it is but if it is anything like my situation I did not get overly concerned.

Have a good evening.

 

[Nunyabiz]

That looks like just basic plant senescence starting, in a week they should be mostly yellow.
Biggest problem I see is a slight nitrogen toxicity.

 

[Gorg]

That looks like just basic plant senescence starting, in a week they should be mostly yellow.
Biggest problem I see is a slight nitrogen toxicity.

This is my first grow run, so I'm not sure what to expect towards the end of the cycle, so I was thinking maybe it had to do something with the age, too. But these spots really confused me. Also the fact that it was only in the area that is closest to the light, and the rest of the leaves elsewhere on the plant have zero sign of this. I would have thought that if it is due to age, the older leaves on the bottom would show it first since they are older, but its only these few leaves at the top.