Generally, I think the reason is the highligts and shadows need a broader range. the reds dont look highlighted or shaded and the armor only slightly so. Id say go nutz with em (not to pure white or anything but you know) and if they end up too high, knock em down a bit. My painting style really has be goin too far one way, then too far the other then fixing everything with midtone washes until its just right. its like a tug-of-war until then tho.
If you are paiting a whole team and dont want to go nuts on single minis i honestly think these look very good. but if you are going for the display effect, you are very much on the right track, its just a matter of the amount of layers you do. the skin is the star of the show here, and on the lips, they are catching so much light that a higher contrast between the edge of the lip and surrounding area might do well. finally, i fancy photo of them is gonna go a long way to upping that score.
anyway, I think it looks good, everything here is done right, it could just use more i think. again, it depends on wether they are display or play.