If so, bypass the softener and see if it improves (you should just have bypass valves on your softener by the head, just turn them).

Also, our softener was old and the resin had broken down, leaking into the pipes. It would plug up the screens. It was exactly as you described--pressure would start off strong, then go down. We replaced it and it improved, but every now and then we still have resin from the old softener get into the faucet screens. It has sucked.