That almost looks more torn than nibbled on. Have they been in strong fan wind, or have you recently moved them around a good bit? However you could have certain bugs that eat along the edges of the leaves. You need to take a good look underneath all of the leaves for catapillars or flying nibblers. Sometimes you can gently shake the plants and any flying critters will fly out. There are some yellow sticky pads that you can get to put in the space with the plants and any flying critters will land on them and stick. I use them to tell me if, what, and how many critters are in the plants. They are called "sensor cards", here is the URL to them where I buy them: http://www.plantlightinghydroponics.com/sensor-3x5-insect-trapping-cards-48pack-p-2220.html They work really well as the bright yellow attracts like flowers, and they are very sticky which holds the critters. You can hang them or lay them down on the soil under the plant(which is what I do to nab fungus gnats)
Did you get the PH issue straight? I meant to check back after I came home from vacation but forgot.
I've got some small clones in one gallon pots that are on a platform up off the floor about 5 feet . . . last nite I was shaking the stems a bit, and a huge cricket jumped out of one of the pots !! What the . . .
something hasta be munching them . . . find it and make it DIE !!