All 4 animals pictured are females. I still have them and they are all laying eggs. You guessed 2 females and 2 males. So you were right 50% of the time which is what you would expect from random chance.

If it works for your animals, great. But to say "I am almost 100% sure you have 2 female juvenile grandis" - just by looking at a picture is pretty bold.

Take care,
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- Joe Farah