I have a 2yr old border collie - she attended puppy socialisation classess and some fly ball sessions. As a puppy if she met another dog she lay down in submission until they had passe. But over the last few months that has changed. If she is off lead and meets another off lead dog she is fine - sometimes she plays but more often than not she just ignores them. But when she is on lead and passess another dog on lead she at times lunges and growls at them. She never makes contact and it can be a small or large dog. sometimes she justs walks passed them. Yesterday she passed a dog that she usually plays with off lead but they were both on lead and she lunged and growled at her. Today while sitting outside a cafe she lunged and growled at every dog that passed. But then ignored another dog when we walked passes it. when she walks passed a dog and doesnt growl I praise her but when she does I tell her firmly NO. It doesnt seem to have helped though. Any suggestions welcome.