I think its more of a combination between genetics and age.
I have 2 pastel females of about the same age and size. One is Browning out terribly, the other is still perfectly clean and bright yellow.
They're both in the 300+ g range and born last September.
The browning out one started changing back in December. So basically right away. The bright clean one hasn't changed yet.
Also it helps to start out with a bright clean hatchling compared to an orange one. Pastel hatchlings with more orange tend to brown out more.
I'll post comparison photos later.
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