The Plant Doctor is in. You water regularly, but wilting still occurs. Poor drainage and aeration of soil. Repot using a lighter soil mix containing more organic matter. Or, if that's not a viable option, increase the number of drainage holes in the container.
Plants are tall and spindly.
Move the containers to a location that receives more sun or light a day. Stop fertilizing the plants, or decrease the amount. Plants have stopped flowering. This may be natural for this variety. If the buds don't open, the cause could be disease and rots.