About a week ago, I lost water pressure to my master bathtub/shower. The toilet and sink in the master bath still have normal pressure. Both hot and cold water for the bathtub have low pressure and the low pressure is a problem for both the tub faucet and the shower head. I'm thinking the problem has to be some kind of blockage in the shower head/tub faucet plumbing since both hot and cold are affected. Any other ideas of what could cause this and possible fixes?