I have a starter and it does not seem to leaven properly. It bubbles just fine when I feed it however whenever I try to bake anything out of it, it just doent leaven properly. Now whenever I try making sourdough bread I have to add small amounts of comercial yeast just to be sure that my bread will rise. Is there anyway to make my starter stronger? If so, how? If anyone has any suggestions I would be very grateful to hear them.