Coki

Hello everyone, I've searched the internet high and wide and this topic was the only one that seems to be referring to the same thing that I'm seeing on my budgie (pictures attached). He is acting otherwise normally: chirps, talks, flies, eats, preens etc. I do sometimes notice watery poops, but they also look normal a lot of the time so I don't know, maybe they're watery after he has veggies or something. Do you think feathers colored like this are a color mutation or a sign of an underlying issue? They were all blue before his last molt, I'm fairly sure. He was hatched June 2020, went through his first molt October 2020, and a second one January/February 2021. I'm not an experienced budgie person, he is my first pet bird. I did my best to do everything by the book. Thank you everyone in advance if you find time to respond with your opinion and I hope you have an amazing day!