I'm defending Carlos's new appearance here and say that him looking alot older than the rest of the cast does make sense. Not only it ties into his mature personality but here's another reason:
Carlos is always frowning, in real life frowning more often can actually make you look older because it causes wrinkles (if you look closely, Carlos already has prominent frown lines ) granted, smiling and other facial expressions do cause wrinkles but there's this misconception about how it takes 17 muscles to smile and 43 muscles to frown (that might be true but other research kinda contradicts that). The point is that Carlos would look more younger if he smiles more but it makes sense that he looks older because it not only ties into his mature personality but also smiling seems to be an indication of Carlos's character development.