Are the eggs in your first post and the other eggs in the next post with photos the same eggs??
The color changing from green/gray to brown baffles me.
Pullets just coming into lay often lay small eggs while their systems fire up. Nothing odd about the size to me.
Your only bird that would lay green is the starlight green layer.
Yes indeed many birds lay before the magical 6 month mark. My own starlight green layers started at 15 weeks. My prairie blue bells waited until 17 weeks.
My leghorns (long ago) laid around that same age.
I have a Brahma that started at 6 months. Said to be a much slower to mature breed but each bird is unique.
To those wishing to debate the issue please start a thread asking how early a bird can lay.....or do a site search as that question has come up often.
This OP had a question that has become lost in the debate. I find that sad.