Hi all. I've got a problem and it's happened exactly the same on my last 3 cycles. Always the same - fine through vegging, nice green colour throughout. Around 2 weeks into flowering I start to get yellowing leaves, spreading througout the whole plant which progressively gets worse, with a lot of leaves going crispy brown, curling up and dropping off. Towards the end of flowering the vast majority of leaves are yellow. Can anyone shed any light on this?

Coco 11 litre pots with clay pebbles
Canna coco nutes - ph.6.0
6 plants in a Budbox 1.2x1.2m tent, 6inch exhaust, 5 inch intake
Feed plants every 3 days
600w HPS

A friend of mine is growing the same strain and at the same stage has No yellowing leaves and much denser buds.

Pics on the way........ they are around 8 weeks flower. I'd like to avoid this next cycle! Thanks!