If I understand correctly, you have my sites in dev that have been copied from production. The profiles that have pictures have URLs that point to production. You have also copied the actual pictures from production to the User Photos library in the dev my site host.
If this is correct, I can tell you what I did in this situation.
Others have mentioned
Update-SPProfilePhotoStore and that is what I used.
During the migration of profile photos from one server URL to another, one can use the OldBaseUri and NewBaseUri parameters. You just need to specify the starting portion of the URL that has changed from old to new and an attempt to rebase the profile picture URLs will occur.
For example, OldBaseUri: http://server1/my/ProfilePhotos; NewBaseUri: http://server1/my/NewLocation/ProfilePhotos
Just make sure that all the pictures exist in the new location before running it.