28 Day Old Budgie Only Has Grey Down

[Reginald 0]

I had to start hand rearing this baby at 12 days old due to the fact the the parents stopped feeding them. He had been making good progress but he doesn't have any coloured down on his body and I'm starting to get worried, the pin feathers on his wings and head have almost fully opened up and he's eating well.

I tried searching for information about this but all I could find was stunting and I don't think he's stunted as he has still been developing.