Upper leafs yellowing

Hi

My lower Leafs seem fine but the new growth is yellowing and stunted.

I've just flushed them with ph ajusted water. no nutes.

Does anyone know wot this deficience is?

Here's a good guide to get you started:
https://www.rollitup.org/marijuana-plant-problems/38772-guide-diagnosing-plant-problems.html