I suggest for your next batch, pick a combination you’ve already done that has the bad smell. (We still don’t know if you were describing rotten fruit or rotten egg smell). Keep everything exactly the same except ferment it in an open bucket / pail / pot with only a towel covering it. Stir vigorously once or twice a day to introduce oxygen. See if that helps the smell. Rack to your jug either after the SG is the same for 3 days below 1.000 (stabilized), or else once it falls below about 1.010.Sounds like primary is a one gallon jug with air lock. Lack of oxygen might be a problem, yes?