Lovely! I like the second series, #3, the best. Upon reflecton I think that's because you've made excellent use of the whole frame (rule of thirds, but on the diagonal) and you've incorporated those ever-so-attractive-to-the-eye diagonal lines throughout the composition. It has what one might call "that professional look."

I wonder if your original image contains more detail in the strongly lit areas of the filly's face. If so, it would be nice to see that detail in this picture. If the detail isn't there in the original one has to assume that the exposure was a bit off. Did you use auto or manual exposure? Check your histogram during this series of shots? Still, quite lovely. Thanks for sharing these.