brownish patches & slightly crispy leaves

[Equanimity]

Hello all.

I am about 28 days into my grow, the details follow:

lemon kush
grown in coir
nutes are canna coco a+b
currently feeding 1ml a & 1ml b into 2 litres of water.
lights are CFL; 2x300w, 4x35w.
last feed was saturday night (may 24) and it was this date when i topped to the third node (they had 5 nodes each).
Temperature rests at around 29c.
Ok, onto the problem:
Yesterday i saw what looked like water (reflective) but it was dry. i moved plants away from lights to prevent a burn.

Today i found this:

This is on all the leaves; it's set in quite rapidly. I'm not sure what to do; I've googled lots and found 8 million different answers and i can't find anything conclusive in the Plant & Pest Problem Solver.

Help?

 

[Antics]

My first guess would be PH spotting, and when I see any problems, the first thing I do is check and adjust my PH before I do anything else.

What is your PH at right now?

 

[Equanimity]

the ph of the most recent feed going in on saturday was roughly 5.9,5.9. i only have liquid testing so i can't test now unless I'm prepared to feed again, which could cause an overwatering and then I'll end up with compounded tangled problems and not be able to pick them apart :/