What on earth has happened to my Dahlia? It was growing vigorously and then it started to diminish instead of grow. Leaves turned yellowy and crisped around the edges. The shop keeper told me to put some fungicide on it, but it did nothing. The only thing that has helped is whacking it off and letting it grow up again from the main stock. The tubers were very fat, much bigger than when I planted it. I thought that was strange. I was going to throw out the whole plant, but when I saw that I decided to replant it to see what would happen. It's growing again. Any ideas? Is it mineral deficiency? Wrong soil type? Potting soil is dodgy over here. Not sure what I've picked up. It's either in Chinese or German.