[Ellie May]

I'd venture to say the daycare is a strong possibility because they both get sick at the same time. I'd hold off from taking them there for a good few weeks and see how it goes. If this is attached to where you work, then clothes and shoes may need to be changed before walking in the house somehow. Showering as soon as you get home wouldn't be a bad idea either. Their sterilization techniques may not be the best...

If it's determined that it isn't this, anything in the yard, etc., then I would be changing diet to something with a moderate protein level and a low to moderate fat level. Not all dogs do well on high protein...