During Ashe's PT she mentioned that Trespasser had new face animations or something, so that might be why he looks different too. Plus it's been 2 years.
Two extremely stressful years no doubt... it's bound to have an effect, just look how getting into office rapidly ages most politicans.
And if the Veil meant that all Elvhen lost their immortality, I guess he's now feeling the effects himself. I guess that Uthenera works by putting them into some kind of suspended animation, so the only way the Ancient Elves we've seen can retain some semblance of immortality post-Veil is to remain in that state pretty much indefinitely.
For all we know, the wizened old elf in the Temple of Mythal that guides us through might be younger than Abelas, but spent more time in the waking world maintaining the temple and so the years took their toll.