Nice work pretzel! The main thing that I see is the perspective on the on the 3/4 angles. I did a draw over, you ideally want these lines to be parallel like they are on your more front facing face.
The other issue that sticks out to me is the top of the nose does not seem to line up on the same center line as the philtrum making the nose look at an angle on two on the left. Its most noticible on the middle head and slightly noticible on the left head.
Overall the structure of these is really good and you are definitely on the right track. Its amazing how just a few small changes can make a big difference on a face so keep up the good work!