Have you seen these people nowadays? Some recasting is definitely in order. Unless they are all playing Admirals.. a ship full of Admirals. Except Kim of course.
Picardo, he could still be the EMH. He looks great and there's all kinds of reasons he cold be older looking. Perhaps he wants to keep up with an older lover, or more likely he gets it into his subroutines that he'll get more respect that way.