Ferret dominance or pecking order?

Question
I had 3 ferrets, and added 2 more about 2 weeks ago.  One of the original 3 has since developed a stress ulcer and had to be treated by a vet.  He is doing much better and is currently being isolated from the other 4.

I suspect that he developed this ulcer because the new ferrets stressed him out.  I am also worried about one of the 2 new ferrets.  I likes to tackle and wrestle with the others - but there is no poop flying or blood shed.  He seems like a bully sometimes because the original ferrets did not play back with him - they would just run the other way.  I am wondering if they are getting used to the new ferret, because one of the original 3 is now starting to wrestle and play back.  I assume they are establishing pecking order.  They have been together for about 2 weeks now, and I was surprised it took this long for the original ferrets to wrestle and play back.  I don't want them to be forced to get along, but I know sometimes it takes awhile.

I have also noticed that the new "dominant" ferret who does all the tackling has been licking the other ferrets' ears.  I have researched this online with conflicting results.  One website said ear licking was a dominance thing, another said it was a sign of acceptance.  What's your opinion?

Answer
Ferrets are not naturally social so no one is being "dominant", they just have different personalities and are figuring each other out.  The play you are describing sounds like normal ferret play.  Ear licking is usually also common with ferrets, we are not sure why they do it exactly, but it isn't something to worry about unless it gets excessive and the ear becomes red and irritated.  Be careful with the ferret experiencing stress and allow him time to relax away from the others if they become too much for him.