Just from those pics, it looks like they're not getting enough nutes, believe it or not. Pale green and slight yellowing of the interveinal areas indicates low nitrogen. If you think EC of 1.8 is too much, how about trying the middle ground at 1.5? I don't see the yellowing that you thought was nute/light burn. Fert burn usually starts at the tips of the leaves and works its way towards the middle of the leaf and stem. I don't think you're going to see light burn from CFL. That usually happens with real hot bulbs, like sodium and MH. Other than that they look good. Great start.