@paqman - The worm castings may be retaining moisture for too long, depending on how much you put in. There is nothing special about worm castings. The nutrients in it are of limited value, it tends to be a bit too alkaline, and it can sometimes be a source of fungus gnat larvae.
Having the perfect potting mix does not guarantee that it will solve watering problems. If the pot is too large in proportion to the roots then the soil will stay wet for too long. Pot size may be the most important consideration, especially since many folks tend to over-pot their plants.
