I get the haze on my blocks too. I've used the Mr. Clean Magic Eraser and it comes off wonderfully. My haze was caused from Versamark, so if you use it, that could be the problem. Just make sure you don't use anything with alcohol in it or it could cause hairline cracks in the blocks therefore losing their ability for you to see through them. Your cleaning scrubber will not affect the integrity of the stamps or the blocks.
HTH,
Becky