Plant was grown in ebb & flow hydroponics system until it failed, now its in a deep water culture unit.

I noticed the leaves were turning Brown/Grey. I thought this may be a disease so I sprayed Daconcil when needed, but it didn't seem to help, so I thought it might be fertilizer burn, so I flushed the system, but now I noticed the leaves are drying up. So I thought it maybe burn from to much light, so I moved the light 2 inches back sideways. but it's still progressing.

Notes:

 * Indoors.
 * Light is 100w 6500K (daylight) fluorescent.
 * Light period controlled by timer.
 * Light period was changed from 14 hrs to 16 hrs after light was moved.
 * next to air vent. (always cold)
 * Fertilizer is miracle-gro 20-10-10.
 * water has h2o2 in it to keep it oxygenated.
 * Air pump keeps water bubbling/moving to keep it oxygenated. (no air stone, just a diy nozzle)