Having dealt with tooth issues/injuries in my one V and one of my fosters, generally if the whole tooth is changing colour (turning a a bit transparent and turning greyish/pinkish) it is due to trauma to the tooth, not food straining.
Its hard to tell from the pic, but the canine looks to me like it is a bit grey/transparent. I would have the teeth shown in the pics checked out by your vet.
Canines are the trickiest teeth to deal with, so hopefully it's nothing major. If there is an issue and it isn't addressed there is the risk of the tooth becoming abscessed, so better to have it checked before there are complications.
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