I usually use a jewlers louper.
Both male and female bellys feel the same. The only thing I can think of that's different is the preanal pores. Males gain the wax females don't. But that's not until they are about breedable.
Flashlights wont harm them at all. Especially if you are shining it to their tail I be never used that method btw. Albinos though are more light sensitive but I doubt you'll be sexing through their eyes. congrats on the babies.
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