Sounds good. I would check the cotton (is it on a lid of some sort so it doesn't get the bran wet?) regularly so it doesn't get moldy. I think spinach is good occasionally, but it has oxalates in it, which can hinder calcium absorbtion. I don't know if it affects leos that way, however, when fed mealworms that have been eating spinach. I would just rather be safe than sorry, you know?
Oh and the white mealworm has just shed/molted. They are white right after molting because their exoskeletons haven't hardened yet. It allows them to actually grow bigger. Mealworms turn darker right before pupating. If you have some that are near the 3/4" size, and they turn dark, they it won't be long before you have pupae. I currently have 16 pupae, and pick one or two out of the colony everyday.