Maybe try epsom salts soak, in case it's a foreign matter type thing? It's so hard to see around the toe, even if you clip all the hair!
Some of MP's previously black nails turned that same transparenty-stripey thing at one point and it FREAKED me out, too. Was told very matter-of-factly that it's just something that happens with age or just because. So, like Judy said, that particular color change shouldn't be an issue.