Labrador Lover

6 yr. old female spayed Labrador at 2 yrs. old.. Noticed a few months ago both of her mammaries starting to sag. Vet found no lumps. Feels like breast tissue as if a false pregnancy starting. No milk. Line of discolored skin between the two from licking – she has allergies we are currently resolving. We’ll give it one more month and consider hormone testing. Has anyone encountered this? I welcome your insight.