I bought some large glazed ceramic pots from London Drugs and have planted wave petunias in them. I planted the same wave petunias in plastic pots that are the same size. I've used the same soil, same fertilizer, same watering schedule. Both get similar light. The one in the plastic pot is thriving. The one in the ceramic is stunted with very yellow leaves. The water that drains from the bottom of the pot leaves a white residue on the deck around the pot. Could the pot be contaminated with something? What do I do? Can I save the plant? Can I save the pot?