I think the problem is only with the black feather. Because you are using RGB 0,0,0 value. And that never happens.
I just searched in google “black feather” and it gives me RGB 20,19,25 in the darkest places.
When colors are wrong our brain immediately notices and says “this is artificial”.
Another thing is: the length of hairs to the left is very similar to the lenght of the hairs to the right of the central “branch”. And perhaps that happens in some specific feather you are using as reference? But I think one side is always much less in length. Take a lookfor example this one. You see one side is half of the other side in length.
Very very well done feathers!