
What a worry. I do hope that Milo will be ok - fingers and paws crossed!
I did a google search to see if I could find anything about the soil - nothing came up really, but I did find this old thread
here. One of the clinical signs listed is a craving to eat soil which would suggest that soil eating is a symptom rather than a cause, although I do agree that it is strange that your other 2 dogs have also had auto immune disease.
That thread also has a link to a yahoo group which may provide more insight.
I also looked for the insurance claim form but couldn't see it anywhere - were you signed in to the site, maybe more options will show up..?
Good luck, and I hope someone with more information will be along soon!