skilady1, I have seven Butterfly bushes around my place here in Southeast Alabama. I've noticed in the heat of summer some yellowing of leaves particularly bottom leaves is common. The first blooms are always the largest for me and the succeeding ones are smaller. I cut off the old blooms on three of the plants and the others I let go. I can't tell the difference in bloom size on the dead headed ones and the others. They just look better with the old faded blooms removed.