They are both MONOs IMO monos can vary greatly from one specimen to the next in color and pattern.
Here are my 2 monos bought from the same shipment and raised in the same tank with the same food one is very bright and well patterned in the other is not but I live it anyway
I beleive they are 12" and they don't look like the same species to me. Look at in the last pic the ones face is more elongated than the others so I am geussing you have some monos and some ocellaris. Just my .02.
Yup 12 inches give or take I have seen a large amount of difference in even farm bred monos not to mention if they where collected from different places in the wild