That's not enough fertilizer to cause the problem. I use soil with the same level and have never had a problem. I have had problems with the lights being too close to the plants though and had leaf curl like you've got. They've always opened up after moving the lights further away. I had LOTS of leaf curl after I added a few extra lights, but didn't change the distance.
6" away is a good distance, but try moving them a little further away, OR try turning one or two them off and see what happens. If the leaves open up after the fact then the lights were the problem (too much, too close, too much heat whatever). You should notice a difference within about 1/2 day of the change. My plants have always been really quick to respond. If not, we can work on it from there.
How much air circulation do you have around the plants? Are the really boxed in or are they in the open under the lights?
If you are concerned about ph levels, you can buy inexpensive testers at most garden centers. From what I've read, peppers like a ph level of 6.5 although I've haven't really paid much attention to it in my plants as they've seemed to be fine with what I'm doing so far.