Grow Mediums Sour crack yellowing leaves HELP please!

[Cheeseman]

hello all. Having a few problems with my Mephisto sour crack ladies.
Week 5 from seed today and the leaves are yellowing slightly and have rusty spots on some of the others.
Currently in Coco 20L airpots watering 4 litres each every two days
Canna coco A+B at an EC of 1.2, PH 6
Any ideas what could be causing this?
Am going to start adding canna boost from next week.
Cheers all,
Cheeseman

 

[TehSnow]

The brow spots on the first pic look like phosphorus def.
Curling/tacoing could be few different things, how hot is it in the growing area?

My

 

[Cheeseman]

Cheers for the reply. I calibrated my PH pen and it was a whole 1 point off, so I’ve been watering at around PH 5 for the past few weeks by the looks of it
The yellowinh and rusty spots are probably down to a deficiency caused by nutrient lockout due to the low PH
I gave them a flush of plain PH 6 water and
now a daily feed of PH 6.2 EC 1.3 with AB and canna boost.
They are starting to green up nicely and the buds are frosting up. 3 weeks left from Saturday so hopefully they fatten up nicely between now then.
Thanks again

 

[Cheeseman]