A spring is mainly dependent upon the source hydraulic pressure. If someone tapped into the spring at a lower point, the water table has dropped, or even if a new, lower opening formed on it's own, flow will be reduced or stopped at all points higher in elevation.

There are other factors, like source flow/volume/capacity. The source path to your spring may have been very small, so it is theoretically possible that it "clogged", though if and where the clog happened, and clearing it, would be a complete crap shoot.