These are great! Nice job capturing the volumes of the muscles. I would pay attention to the necks & heads, as they feel less realistic than the bodies. The heads are all a little on the small side and the necks too thin. If you can bring the necks/heads up to same level of mastry as the bodies, these drawings will be FANTASTIC!
Hey SapphicFrog, you are on the right track and you've given birth to some nice creations. What I'm going to suggest is that you join my study group hahaha, no. What I'm going to suggest is you avoid using shadows or if you do try and think where the light comes from and if it makes any sense. Some images can be very lucrative to study because there are often more than one light source which can make it hard to see. If you do study images try and find images that have a clear light source, some more volume to the subject often makes it a lot easier to see what's underneath (e.g: Body builders or people with a few extra pounds). Also try and keep your shading pattern, being consistent with the way you shade makes it more appealing automatically.
Things you can keep in mind when you're asking for critique next time could be:
elapsed time, goal and possible things you think are wrong and what you like about them.
hope this helped!