Test your soil PH if it's to high or low the nutrients will lock up. Weak plants are susceptible to all kinds of bad stuff like viruses, molds, bugs etc. Remember the growers pledge..KISS...Keep it simple stupid..........Too much worm castings will plug up the soil by holding to much water and locking out air. Worms eat organic material and lots of it so putting them in the pot opens another can of worms...i couldn't resist. Air in the soil is as important as any other component too much or too little and you got trouble. Good luck.