The pot is very large and that makes inadvertent over watering more likely. Overpotted plants tend to put more of their energy into filling the pot with roots at the expense of top growth. So, be patient.
Fertilizer is not medicine and is intended for use only on plants that are healthy and growing vigorously. Plants use nutrients in very minute quantities and not at all when they are not growing or growing very slowly. Manufacturers want you to buy and use a lot of it so they promote its over use.
