Applejack is the only one that isnt that great, it seems "off" but it could be that im not used to her hair being like that. I like how the elements arn't just necklaces but i dont get what Pinkie's is for... All up I like it!
Love the way you made the Elements jewels into different pieces of jewelry for each character! One thing I would suggest is working on the facial shapes for each character; Rarity, for example, has a more angular, pointed snout than drawn here. Overall, I think you captured each pony's personality perfectly. Great work!
Although I love Rainbow Dash's mane, I don't really like her outfit that much. I dislike her outfit because the dress to me makes her look a little too girly. Maybe giving her a uniform like a Wonderbolt would be more boyish on here. On another note, I love the rest.
Who wears a dress to a battle? A typical "magical girl" outfits are alright, they're decently easy to move around in, but good Celestia, these look so impractical! Especially for Fluttershy and Rainbow, who will almost certainly need to fly. I will say that I like how each girl is wearing their Element differently, though.