I don't really know, Lucille, but I would imagine they're just like people. Sometimes it's the little runts who have to make up for their shortcomings and inadequacies by being antagonistic and snotty. Then there's the larger, more confident ones that don't feel the need to prove anything. Of course you'll get a bunch of in-betweens and exceptions (like people) but I think that's often the case. My sheltie was tiny by breed standards, but in her mind she could have put a rottweiler in it's place. My golden retriever could easily eat my dachsund, but she allows him to kick the crap out of her. I think the little ones usually commit whatever the big ones let them get away with, and it seems the big ones don't always feel the need to exercise their physical advantage--They know it, and that's good enough. Perhaps that's why I'm becoming more fond of the larger breeds...
Anyway, I do think having them all fixed would help any aggression you're witnessing. I would assume all four of them are battling for position right now after the two recent additions. But, I think that if the "real" alpha (you) keeps a firm foot down and reminds them that you're not going to tolerate any funny business from them that things will inevitably calm down. I don't want to under-appreciate what nerves and chaos you're experiencing right now with the four of them getting used to things, but please remember that if you want them to keep their cool, you have to. I've been learning it the hard way myself, and I admit that my patience wears pretty thin at times--especially when I'm running on little/no sleep. What seems to work well is reinforcements of both extremes. When they're being good, be overly praising and appreciating. When they're being rough/naughty, put your foot down, raise your voice and issue a "time out" if needed. They need to learn what's acceptable and expected of them as well as what is not. Some of the worst-behaved dogs I've met come from homes where the owners feel too guilty about disciplining them and let them get away with murder. I reckon some human children are affected the same way. You have to have boundaries and limits. You also need to carefully administer the praise and affection that they so desperately seek. There's no overnight cure for unruly dogs (or people, for that matter) but the more effort you put in now, the easier and smoother things will be in the future. If you find your fuse running short, pen them up, let them know that they have you ticked off and go for a walk by yourself. I firmly believe that guilt can go a long way with getting through to dogs when they're not respecting you. I know it sounds pretty harsh, but it is your responsibility as their owner to keep things in order. They need to know that you fully intend to exercise that responsibility.
I hope that at least makes a little bit of sense. It's basically what I've been telling myself for the last few months. It WILL be rough, but how you react and respond to their roughness will make all the difference in the world. Rest assured though, it's definitely worth the effort. If you ever need to talk or just sound off about things, you have my number. Keep us updated.
