try black light on the adults, sometimes this reveals near-invisible patterns in BELs. i mean, dont give them sunburn, just inspect them for fluorescence. if you see a difference there, maybe you see the same difference in the offspring.

or you could breed it to something else from the BEL complex, a super phantom/mystic, or a super mojave, then you can tell the babies apart. super mojaves have the grey head and are also cool and in demand, and mystic potions are nice