I have just taken our 2yr old cocker to the vets for his booster and health check. Whilst there, the vet (not our regular one) said she had detected a heart murmur, to which I expressed great shock as this has never been mentioned before. She said amongst other things which tbh I didnt really take in, that it could be ''because he is a very fit dog''. 
I mentioned a problem he is having of an odd lameness in one of his back legs/foot - he intermittently lifts his foot for 4 or 5 steps then puts it down and carries on normally. It only occurs when he is ''trotting'' off lead, not when walking on lead nor when running full pelt off-lead. As far as I can tell I cannot detect any sign of pain, and as much as he will let me, I have had a good squeeze and stretch of his leg from top to bottom. He doesnt show any outward signs, merely ''lifts'' his foot as described above. She had a cursory look and decided that as he was very tense (her words, he seemed fine to me) she couldnt examine properly and said they would have another look at it in six months, along with another look at the heart murmur.
My question is, should I leave things as is, try and put it out of my mind for the six months, or ask for a second opinion with a view to an ecg or whatever appropriate straight away for the heart murmur, and a better examination for the lameness? Not wanting to undermine her, but the fact is our regular vet has seen all our dogs over the last 15yrs or so, I trust him implicitly and he is extremely thorough. This vet I have never seen before, seemed quite unsure of herself even nervous, and frankly did absolutely nothing to put me at ease, quite the opposite.
Am I over-reacting? prepared to be told I am...but if these two things could be problems which should be looked into further sooner rather than later, should I push for this?