All of a sudden my pup has almost completely changed ... Is this common ?? She will be 8 months old on the 18th of June , her retreive was excellent , her recall was excellent , now it's like I've never taught her anything when I call her in the garden she just lays down and wags her tail and runs off or just completely blanks me , is this fairly common in pups of her age , really getting frustrated with it , by the way she is ... Sal/grey x sal/deer/bull-collie-grey cheers