tin foil is a very bad choice as a reflector it bounces light in all directions white is the best reflection and also should be using some compact florecents or the t5s they work great and give off better light then the cfl bulbs too
ya sounds like a fertilizing problem to me but the leaves r mutant just like mine i had one fan leaf that had 12 leaves on it was un reAl and they are growing insanly fast and the leaves all around r just gigantic but the yellowness if from fert for sure