TMNT practice comparing

On the left there is one of my first pictures of TMNT i drew even without reference. Leo an Mikey were drawn first time there... Donnie and Raph were drawn second time. My first picture of Donnie ever is here:

And Raph's first picture here:


But these are simply without reference and so it came out even worse :/ It was drawn on April 14th 2013... And today's night i decided to draw it again to see if i improved and so look at the right side where is today's version, aka drawn on August 16th 2013, so over 4 months later... I still think i have some problems with drawing leo's face and its mroe about luck if i draw them well or worse so im still practicing.