What deficiency is this?

I am pretty sure this is a deficiency of some nutrient but not sure what.

I am growing in amended soil from buildasoil (2nd full grow in it), blumat watering, stable temps at 82 day / 76 night, and stable humidity at 65/60. Sealed room, co2 @ 1800. 1250w HLG lights over a 4x6 area.

Any suggestions on what I can do at this point? It is week 1 after light cycle change to 12/12

IS it coming from the bottom ? It’s important to check if it’s mobile or immobile nutrient. That will help to diagnose problem

Ryuazki said:

IS it coming from the bottom ? It’s important to check if it’s mobile or immobile nutrient. That will help to diagnose problem

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only the upper canopy. nothing happening on the bottom fan leaves

Dryxi said:

only the upper canopy. nothing happening on the bottom fan leaves

Click to expand...

Then imho it looks like Fe(iron) defiency.

Could be P or K but then it should start from the bottom if i remember right because it’s mobile nutrient. I would wait 1-2 days and check how it develops or check for bugs in mean time. Always better to wait a while and be 100% sure then do something in hurry