Cuckoo Silkies with brown spots in their eyes

[Cloverr39]

I tried doing a bit of research on this, but every post I could find suggested a completely different cause for dark spots in the eyes like this.
Last year it happened to a cockerel completely unrelated to the ones it's happened to this year. It couldn't be an injury, considering it is happening in multiple different birds. I saw a version about excess melanin in the eyes? Or it just being a normal eye color defect? Could it be happening because of breeding brown eyed birds with orange eyed birds? I don't think it's mareks because the Iris itself is still perfectly round, there are just those brown spots all around.
First 2 pictures are of one cockerel, other 2 are of another cockerel. It's less noticeable on the first one.

 

[Cheekychook11]

Are they acting normal otherwise? And if they have always had it, probably just natural eye colour but I’m not too sure

 

[Cloverr39]

Are they acting normal otherwise? And if they have always had it, probably just natural eye colour but I’m not too sure

Yes, they're acting normal. I actually think they hatched with brown eyes that became orange over time, just like how their skin color lightened with age.