How strong of fertilizer are you using, Charity? You should not see salt buildup with such an infrequent fertilizing schedule (assuming you water at least once a week in between the times you feed.) Other than that, I think I would recommend leaving one of them alone and let it grow in its pot while you continue on schedule with the other. Since you have two, see if repotting really was the issue. Make sure they both get really bright but filtered sunlight and lots of air circulation to help them dry off after you water. Good luck!

cheers,
BD