Phalaenopsis leaves mottled
 

At first, I thought this might be crown rot. I read online to pour peroxide in the crown and it would bubble. It didn’t bubble, so now I am wondering if something else might be wrong. The leaves seem to have a grayish mottling on them. The roots, however, look very healthy.

Any ideas on how to save this orchid? I do have it isolated just in case it might be contagious.

I can't see well enough to be sure, but it reminds me of spider mite damage, scale or mealy bug damage and salt buildup from using water high in dissolved minerals.

It looks to me a lot like hard-water residue. If so, you can clean the leaves with a half milk-half water solution, or a bit of lemon juice diluted in water. (use a cotton ball, or cotton swab... softer than a tissue or paper towel, you don't want to scrub) If it comes off, great. If it doesn't it could be pest damage, and you'd need to make sure they're not still around,