Yellowing leaves mid flower

[HandsomeJohnny]

Here goes...

Problem: yellowing sugar leaves

Medium/grow method: 50/50 perlite/coco, wilma 11l pots

Feed: and supplements used: canna coco a/b, rhizo, cannazym, boost, pk 13/14. Res ec 1.9 ph5.8

water source: tap, dechlorinated

Strain/age: Royal Cookies auto, 7/8 weeks ish

light used: hps dual spec 400w, cool tube with 5" fan

Climate: day 26-28deg c night 18deg c, rh 45-50%

Additional info: some slight canoeing on top leaves of other 3 plants. sugar leaves have yellowed over the past 3 days or so, any advice greatly appreciated!

 

[namvet25]

Make sure there not to close to the lights.Feed full dose of flower nutes along with calmag every week.Some leaves will yellow naturally at this stage so not to worry.

 

[CBgrower]

Looks like light stress IMHO.

 

[Machamillion]

Back light off and pk is your friend.