What is Going on with my Kids

I know I am far from a perfect parent, as seriously is there really such thing? But I always thought Chris and I had control over our kids and they were not that badly behaved, and I think this is true but recently things have gone down hill and I'm struggling to understand whats going on. We are having that whole Taylor issue, which I will say we have noticed a change in her since her change in diet. BUT now for Masie to jump in and have her go, but hers is a lot worse. She has become a BULLY, and I'm very upset, angry, sad, concerned and disappointed as a mother.

When HAILEY is my angel, I have to realize I have a problem! LOL, joking.

OK so a little bit of what is going on, Masie has started up with this huge attitude and answers back to everything in the "I don't care" voice. She is being spiteful to her sisters and physically harming them at every chance she gets. Just today I hear Taylor screaming and I go out there to find Masie and Taylor covered in scratches and small cuts. Taylor wanted on the trampoline and Masie wouldn't let her so Taylor came on anyway, and Masie attacked her! So of course Taylor attacked back. They were both punished and grounded (Taylor of course screamed the house down, but surprisingly calmed quickly and accepted that she was in the wrong too). Masie was grounded and had to write an essay about whats been going on (ill post it at the bottom)

I have a daycare girl that I take to and from school, she is in the same grade as Masie and they have always got on reasonably well. One day when I picked her up she was acting strange, sad, guarded. I asked her about it and she said she was tired. A little while later she was still the same and I asked her if she would like to talk to me about whats going on, she said yes. Basically she said she didn't want to be here as Masie is so mean to her, she said and I quote "she thinks she is better than everyone and its not right". When I comforted Masie she said that its all her stuff so she gets to control it!! Seriously, oh no way little lady. The daycare child then said I spoke to Faith about it and she told me not to worry as she said Masie is changing lately and is mean to everyone. I was upset by this as Faith has been her best friend since Kindergarten, and although they are still close friends, they are losing their bond.

I have had conversations with Masie about this and confronted her many times about where this type of behaviour will put her in the future but it doesn't sink in. I don't know what to do, my former popular, sweet lovely girl is turning into an ugly bully and I wont have it.

I don't want to make her be nice, I want her to WANT to be nice, any ideas?? Phase? Pre-teen? Just a girl? Completely normal? Power trip? Is this happening to your child?

Masie's Essay, that I made her read out loud which was very hard for her and embarrassing, I hope it did something.

I am sorry for being mean to everybody.
I am a bully and I don't like it.
I am sorry for the peoples feelings I have hurt.
I will try and be better.
I will try to change my behaviour.
I am sorry I wont be a bully again.
Masie

I just went in to say good night and hugged her real tight and whispered in her ear "bring my sweet Masie back" and she burst out crying and said she was sorry. I told her being this age is hard and so many things are changing and I'm here to help her adjust! She said she didn't like being this age, but when I told her I loved her being this age as we can talk, sit on the garden swing and read together and hang out in the coffee shop drinking Frappes she smiled and agreed. I think I have made a break through tonight but need to keep up with this strict parenting until she understands and we can maintain.