"Seasoned" is right about the fan. It will make your plants stronger and less likely to topple over or break when budding.

A flouro can burn a plant, especially when it is just starting. Usually it is a combination of light and too much nutrients though. This happened to me. Sometimes when a plant is on the edge, a little more light will push it over the edge. Reduce one or the other and symptoms may go away.

I don't think light in your case is the problem. I would flush out your system as well and as much as you can stand spending the time. Flush with PH adjusted, chlorine neutralized water. Then feed with nutrients 1/4 the strength the manufacturer recommends for 2 weeks, and see if the yellowing happens on any new growth. If not, increase food very gradually each feeding until the first sign of yellowing appears, then back it off some.

Keep your reservior airiated and preferably moving. Keep your nutes at the proper temp (about 78F), and PH (5.2), and chlorine content (none).

If you carefully follow my advice and the symptoms persist, I would be very surprised. I also wouldn't know what else to try.

Good Luck