Dark mottled spots and yellowing all over?

Lemon OG haze day 59
600w duel spectrum 16" from top
Temp 29c RH 48%
50% coco coir 50% biobizz allmix
11l square pots
Canna aqua flores
Canna boost accelarator
Canna pk 13/14
Canna cal-mag agent
Canna ph- bloom

Yellowing started a few days ago followed by a few dark spots. I flushed them with 15l of plain water and gave it everything above total EC 0.9 PH 5.7. The problem continues.
I'm wondering maybe the PH is too low and locking nutrients out, has anyone grew in a 50/50 mix of coco and soil that can help me?
Or is there another problem that I haven't noticed?

http://www.growweedeasy.com/manganese-deficiency-cannabis
ive never used coco soil before but the ph seems a little to low at 5.7

I'd say she's hungry and wants more food I give my clones 0.7 to 0.9 ec you should be around 1.2 minimum at this point

Thanks for the info. I have flushed them again 2 days ago with tap water ph 6.5 I will give them a light feed tonight. I'll up the feed if I see some decent growth. I have noticed the tips are burnt a little so I'll try less of the extras and just give her Flores at a ph6-6.5.