It could be over-supplementation from the pellets. They aren't meant to be fed as the sole source of food for a bird, getting them to eat 70-80% pellets with the rest being fresh would be the most ideal for your bird.
It may also just be a normal variation in his feathering. Does the rest of him look okay?
If he's acting normally and it's just those feathers, wait and see what he looks like after the molt. If he hasn't had an annual exam with a vet that's always a good idea, especially if he spent any large portion of his life on a seed only diet.Hi Milo, His feathers looked like this when we got him when he was on a seed only diet. The rest of his feathers (on his neck and chest are fine). He's also going through what's looks like his molting phase.
A picture isn't something that can help diagnose that unless it was something like PBFD which has a specific presentation (which this is NOT)Thank you so much, its not any kind of feather disease is it?