Welcome and it sounds like you have your hands full !! I used to have border collies and they were rather touchy also, they are just too plain smart and want to train thier human perfectly. I have a huge black lab Lucifer, a little yorkiepoo GUapo and my Poochon Sophie. They get in little spats but nothing serious and since Lucifer is the baby, even though he outweighs the others by over 80 lbs, he is low man on the totem pole and I actually think he doesnt know he is big At least not when he is tattling on Sophie and Guapo by leaping into MY lap. Hopefully for your sake the dogs will learn thier positions in the household and things will settle down. GOOD LUCK