[Britster]

SD = Science Diet.

Are they eating anything else at ALL besides the SD?

Dogs can definitely make themselves ill when their owners are gone, but it sounds like this started before you were gone if I'm reading correctly?

So what are they eating now? Hamburger and rice?

Maybe a Royal Canin RX formula would be helpful in this situation.

I somewhat recall them eating Natural Balance in the past -- they have some very simple formulas, that may help.