Sugar leaves turning yellow on upper buds only

Hi,

71 days since flip, starting week 11

I wonder why 2 plants getting top sugar leaves bright and yellow?

I have 2 weeks left, not sure if it so important now, but I want to learn from it.

I don't think its a light burn (I had some UV light issues on the right plant, but its not having this issue) but then again its only on top buds

Its the 2 left plants on the photo, the right one is getting yellow but no sugar leaves, the 2 left ones are getting some yellow sugar leaves.

Thanks

Anyone?

it does seem to resemble light stress. What is your set up? But at day 71, you will often see some genetics that fade out.

I have 2 150w led boards, in 3x2 tent
The led on the right is UV.

Just worry that its not something else...