Need help identifying issue

[PuravidaC]

Have had a string of grows with reoccurring issue. Have yet to figure out the problem. You can see there are brown areas between veins on the lower front leaf, although area shown in photo is not as brown as real life (best photo for my camera) and tip of leaves are cupping up (far left leaf) and wrinkled (far right leaf).
Grow specifics: 16 day old photoperiod White Widow grown in coco with perlite in a 5 gallon fabric pot. I start my plants out under CFL and switch to LEC after 3 weeks so all this has had so far is CFL. Following Nebula's coco feeding schedule. Have not seen any pests but brown spots have been the recurring issue. I know from experience that brown spots will spread and take over entire plant. If I can't identify issue this will be my last grow! Thanks in advance for your help.

 

[Sww]

I first grow In coco my plant was curl up to keep moisture and took out the perlite and much better. I think a fibre coco and perlite be to much

 

[HappyDaze]

Did you condition your coco? Looks like Calcium lockout and or K toxicity... your sig says you're growing in FFOF, which is pretty rich out of the bag. If you're feeding on top of that, you might be overdoing it.

 

[HappyDaze]

The opposite is true....you need enough perlite (25-50% depending on container size) to loosen the coco so it doesn't matt and screw up your drainage.

 

[PuravidaC]

Always grew with FFOF but trying coco with 30% perlite this grow. Haven't bothered to change signature. Yes, I conditioned coco with cal-mag and low level nutes.

 

[duckman]

I don't see any comments on the pH...everything okay in that regard?