Giesel x Chem91 Yellowing of top leaves

This is Giesel x Chem 91 on day 54, in soil. Only top leaves are doing this on two of four branches. Lower leaves look good.

Anyone know what this yellowing issue is? All other plants in tent look good. I am terrible at looking at leaf deficiency charts.

Chem 91 crosses definitely get tricky in flower. Not worried about it but would like to sort it out to improve future runs.

How close are the lights? Might be the beginning of light burn.

Dark green leaves with claw and burnt tips suggest N tox.. How much have you fed?

Johnny15 said:

How close are the lights? Might be the beginning of light burn.

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Plant is 20+" away from a QB that is pretty dimmed. It is the plant furthest from the light, but light stress/burn could be an issue here. Thank you for your input.

HydoDan said:

Dark green leaves with claw and burnt tips suggest N tox.. How much have you fed?

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Could be N toxicity. I am running organics and have moved to low N nutes for flower but did use a 5-5-5 as part of a tea a few weeks ago. I keep EC at 1.3 or lower and the last two feedings have been around 1.0 and low in nitrogen. Thank you for responding.