There's no such thing as pre-existing conditions on employer-sponsored insurance any more.
There is a thing called market compression. It means that people who have been in the job for a long time are often paid less than people who have joined the employer more recently. It's got nothing to do with your veteran status and everything to do with life as we know it today. If you weren't disabled and weren't a veteran the same thing would be happening. I won't even try to tell you it's fair; clearly it's not. But the law doesn't give two hoots if something is fair; they only care if it's legal, and it is.