HI there and thanks for the question
This is a hard question. The problem is that you are not always there to reprimand them and reinforce your position over the dogs.
So i think each dog is slightly different? Do you walk them in groups because this does make things harder.
So some basics. I would recommend getting some Gentle Leaders or Halti's to try. I have 2 for my dogs and they are absolutely brilliant. The way they work is by pulling the dogs nose to the side - so instead of pulling against their entire weight you are only pulling against their nose. This makes it much easier to control them and much more gentle on your arms.
When they do misbehave you do need to tell them off ASAP. Give them a yank on the lead and a loud GRRRRRR or AHHHHHH. If you want to try and carry a water pistol you can give them a squirt but you might not have enough hands.
Then make the dogs sit. Wait until they are relaxed and calm before carrying on.
It is also important that you notice when the dogs are getting worked up. If you see them getting excited make them sit and wait for a bit. This will shortcut the whole thing and stop them getting over the top.
If they do nip you reprimand them as i mentioned above and make them sit.
I would try if you can taking one for a walk at a time and then as you control this one slowly walking more and more at once
Todd