Mutilated new growth, help!

High,

I have a pic of my veg setup below, along with the two problem plants. They have been in veg room for 2 weeks, just moved from cloning. The new growth on two of the plants is looking really deformed and mutilated however, which concerns me. My inclination is over-fertilizing, but I want a second opinion. Right now, they're getting watered 3 times a day for 3 hours each time on a drip system. I am using a half-strength solution of Advanced Nutrients Sensi Grow A&B (at least I think, the directions on the back telling how much to use were a little unclear). They are under a 400 watt MH bulb, and I think getting enough air circulation. Any thoughts?

 

This is my first attempt at growing and hydro minus the parent plants that were grown up in soil and are sitting next door in flowering room. I desperately need some help here, don't want to lose my crop. Some of the other plants have thinning leaves as well. The pH level seems to be rising most of the time (I am guessing b/c the tap water I use to top off my reservoir is around pH 7.0), so every now and then I bring it back down to about a 6.3. Is it crucial that the pH consistantly stay at this level? If so, what is the best method of monitering and keeping this level? Also, I am wondering if it would be worth my money to buy one of those TDS electronic dilly-doos? If it's not necessary, what is the best way to add nutrients accurately?