i'm seeing some hesitation in your linework; especially your 1min / 5min ones. try to draw with one line instead of making it sketchy for your longer poses-- forcing yourself to commit to a single stroke for an arm or leg or hip will make your choices more deliberate and help you improve. also, try to avoid shading if you can. shadows allow us to hide our mistakes when figure drawing! but your b&w value study is good, you should keep your shadow work to those studies so you can develop anatomy skill and light/shadow skills seperately.