basically, far as i know, if its heat stress, simply move the light a lil higher.
i dont think a reflector makes any difference in that respect.
hold your hand open, palm up at top of the plants. if you 'feel' the heat and cant keep ur hand there for a min or so without feeling the heat, move the lights.

if u move lites too far, worst thing that can happen is they stretch a lil, then readjust.
if they are too close, they fry

if all else fails, maybe go post up and let Stitch take a look.

good luck!