Hi, When I take our 6-year-old chocolate lab out for a walk, every now and then he will slow down and walk at a really slow pace. When he does this it can last for 5 minutes or so, and then he will be back to his normal walking pace. He's been doing this for a while now and his recent one looked quite bad. He slowed down for almost 10 minutes and anyone else would think he was 12-years-old with hip dysplasia or something. Has anyone else experienced this behaviour before? Should I be worried? Thanks!