A couple of thoughts. First, this has been a very unusual year. Some producers who tapped very early (with vacuum) had record yields. Others who tapped later, even with vacuum, are short. A lot depends upon location (elevation, aspect) in addition to when you tapped.
Second....how old is your tubing system? That can have some influence depending upon other things as well. Slope won't have much of an effect with 5/16" tubing. On gravity, sap will not run after a few days without a refreeze (which we've not had for a few days) regardless of the spout you're using. With a gravity system, annual variation in sap yields tend to be far higher than with vacuum.
Third.....last year was a record production year for most areas in the northeast. Unlikely you're going to match that again right away.