I think I'm going to end up in the vets with this, but there are so many knowledgeable people on here I can't resist asking you first.
I picked up my lovely labs (nearly 9) from the quarantine kennels in Sydney on Saturday. They had been there for 30 days. 
They were very excited (understatement) to see me and were fine on the drive back to my house here in Aus - 1000km from the kennels. It took 12 hours to get home, they slept lots on their lovely new beds and played lots on their first day here - including in the pool.
Today the dog (Jack) is just not himself. His tail has not wagged all day (not normal at all) and it is just droopy. He seems bright enough in himself, keen to eat, drinking and weeing normally, just no wagging, and he is v.sensitive of his bottom.
Could it just be the change in diet from the no doubt cheap shit food that the kennels fed him back to RMB?
Am I just jumping the gun, could it just be that he needs a few days to settle in? (The bitch (Jill) is completely fine, couldn't be more normal)
I love them so much. Hate it when they're poorly 