Is it possible for eggs to develop at different rates?

[j'schicks]

Is it possible that my eggs (which came all together, look identical, and went into the bator at the same time) could be developing at different paces? When I candled on day 7, I only saw development in 5 of 14 eggs. Today, day 11, I think I see development in 7 of the 9 which looked clear on day 7. These 7 eggs look like something is happening but they don't look as developed or as large as the to-be chicks in the 5 which showed development initially. Thoughts?

 

[flgardengirl]

Yes if you have hot or cold spots in your incubator, some could be more or less developed

 

[j'schicks]

Interesting. Should I rotate the eggs around the bator or leave them where they are?