Last year I planted some petunias in some window boxes that hang over the railing of my balcony. A few weeks later I notices that the plants were kinda sticky and felt weird. They died shortly after that. Does anyone know what this could be. Also, If a plant does have a disease, do you need to sanitize the planter before putting new plants in them? Even if they container was empty all winter? Is so what can you use to sanitize them?