Dave, don't be too concerned about some of what you think is premature yellowing, especially on Orientals. Bulbs are doing what they do. If they don't need the leaves or if weather conditions are such they can't support them, they'll drop a few. That's normal. Then too, if the lilies in question were just planted last fall or this last spring, they're not fully acclimated and are living according to their previous locations climate schedule and time clock. Also, be aware that all smaller growth around a central plant such as offsets will always turn yellow and go into semi dormancy first before the larger main bulb does.