[jimbosan]

Could be one of several things, there could be a leak in one of your pipes or your neighbors, a neighbor my have increased water usage, the well and or the pump may be aging to the point that pressure is affected, there could be lime build-up in the pipes reducing the inside diameter. I doubt that you have roots growing into any of your water supply pipes thats something that usually happens with waste pipes like sewer pipes and septic laterals. You might want have a plumber come out and take a look. Like I said it could be one thing or it could be several... Good luck!