It's probably not one exact thing, but is really just what your coach is saying: you are working too hard, so don't do that. Relax, and just let the movement carry you. Dancing is not a foot race, after all. If you've been developing your technique then what you need to do is probably all there (or there enough for what you're doing right now), so don't overwork and overthink it, just dance it. See how lazy you can be and still produce the dancing you want.