Dropping bars

I set up a jumpers course that was used at our clubs spring trial. It was a novice course. I walked it and then ran Miley just like if we were at a trial. She dropped several bars. She is taking off to soon and I'm not sure why. She did this several runs in a row and then she seemed to fix it. Do I need to do some jump chutes with her? I don't have the room to practice at home like I do on this club practice field. Is that the reason she was taking off to soon. She has so much more room to run and is just to excited?? She missed a few jumps going wide but that was my fault. I also need to work on "go on" , she didn't seem to understand that command at all.