I don't really see a problem with Irua, aside from the fact that... she has a busty chest for being fourteen? (Looks busty at least to me.)
Aria has problems that I saw right away however...
Having taken it into paint, there is three "white" instead of transparency pixels close to her right side armor, I'll show you later.
I have circled the spots that I feels like are problems, but I am novice, so I don't really have proper insight.
The circled area on her hair feels like it's... awkward? I'm not certain if it's correct term to describe it, but I feels like the hair doesn't feels like hair but rather a mess of pixels. Perhaps an expert could tell you in more details, or at better explanation.
The circled area on her armor need shading. That is for certain.
And lastly, her left side armor is flat, make it rounder.
Perhaps there are some shading you need to do that I didn't notice for Irua, so it is a good chance to check her shading yourself.