Thanks for pics. No, I wouldn't replace the remaining ones; they appear to be in good shape. Even this one might be repairable with gluing it back together if your glue game is good. It's just the nosing broke off along the grain.

But, it also looks like it's easy enough to get the old tread off and replace it with a new one of the same thickness. If the thickness isn't the same, then it will be a forever trip hazard.