My chicks are seven weeks old. They have NOT been in their chicken yard because it's not quite secure just yet. I'm hoping to have it safe by this weekend. While I have been working on the fencing, the grass has grown tall and has fallen over. Should I mow it before I let them into their enclosure. It's about 22 feet by 22 feet. In other words, if they eat the tall grass, will it be harmful?