Just wondering what happen to the 5 year rescue you got back in March, I know from reading your prior post you were disappointed in her lack of potty training , then I noticed you didnt post any pictures, did you end up getting rid of her, or perhaps , the biting is because you have added two new dogs since March... sometimes they get territorial and may just be biting to protect you and or your home and not from aggression?
My little one always gets a little territoral around new dogs but it doesnt last to long!!! Sometimes its just a little confusion and they get over it.. Good luck would love to see pics of all three of your new rescue!!!