When Your Pets Start Losing Control
I'd get a full blood workup and toxicology report, something is affecting them and I don't think its animals outside or marking as they are both older...but not terribly old.
Have you specifically addressed this issue with your vet, or were they just regular check ups? You need to first determine if this is behavioral or physiological, then go from there. If it is the former, retraining will be required. If it is the latter, medications/supplements may help.
Is there a possibility of low grade bladder or bowel infection or cancer?
Has there been a change in the food you give them. Maybe another type of food will improve their habits.
My present dog is a lab/springer mix going on 17 years. Yeah she is losing it but weve been more vigilant about frequent trips outside.. Once she does her duty inside the house then she has marked her territory and the remaining odor reinforces her inside habit. The odors must be completely removed to break the habit. This is one reason ive never let any of our dogs on the carpeted part of the house. Kitchen and laundry room only. Text
Sometimes dogs urinate or deficate in order to establish their territory. You may want to look around outside for any evidence of midnight visitors. Maybe racoons, coyotes, other dogs...etc. It could be that their scent is around your house and is upsetting your inside dogs.
If you see no outside evidence, maybe installing a security camera by sliding glass doors or windows will let you know what is going on.
If you do have some midnight visitors, you could try installing a motion activated sprinkler. Visitors comes up at night and gets wet, then goes away and probably won't return.
You've already done the responsible thing and taken them to the vet to see if it was physical. Now check and see if it is territorial.
Good luck to you!