I can't get the pics to enlarge but there are a couple things I would check. Your nutes and conditions sound fine in theory but there's three things about the pattern of damage that make me go hmmm...
1) Splotchiness and evidence of desiccation on the leaves. Are you certain that you don't have mites? I can't enlarge so it's hard to see if the splotchiness is more like little white freckles. Check for tiny webs/eggs under the leaves and chew-marks on top.
2) V-shaped tipburn. You flush often/recently? Usually I see that and say 'soil salting!' but combined with the other two factors it might not be so simple.
3) Severe down-curling of the leaves. Usually that indicates either nitrogen overdose, suffocation (but you add CO2), or a problem with your roots in relation to their home. From here, your pot size looks big enough but your soil looks kinda wet. What's the drainage like? ESPECIALLY with used media, I'd add EXTRA drainage, including perforations in the SIDES of the pot. When I grow in any pot over a gallon I make sure there are several 1/2" side holes drilled a few inches from the bottom to help air circulate better. This will also help you prevent or heal the dreaded root rot. If you have root rot, the plants will act root bound and wilty. If you have areas in your soil that never dry out, the plant can't use them, and will also act like it is rootbound.
I'm going to add that if you ever re-use media, it's not a bad idea to spread it out to dry completely before you use it again, and even bake it in the oven to sterilize. Whatever you do, make sure that you let your pots get quite dry between waterings. Fresh coco is difficult to over-water, but as you get into some older media that has decomposed a bit and has root particles and such in it, it will start to behave more like plain ol DIRT, lol.
Oh also, if your plants are sitting in trays, make SURE that when you water to runoff, they never sit in the runoff water. Prop them up on something to prevent that.

Summary:
-Check for bugs
-Avoid re-using soil indoors, put it on the veggie garden
-Give good air circulation to the root zone by adding drainage and holding back on water