Imaging lines on boards

We are trying to image fine lines on copper and double treated material. We are not having all of the images being developed all across the board. I've used the Riston 25 step scale getting a reading of 13 or 14 but all of the resist is not developing off. We are using MM550 from Dupont and have a 1% by weight of Sodium Carbonate Monohydrate. Any ideas would be greatly appreciated.