I have always had good blooms from my clematis, but this year Nelly Moser only had one bloom, Ville de Lyon has no blooms, Ernest Markham has no blooms, and The President has no blooms, just healthy green growth. They are all 10-12 years old and have always done well. I've been taking better care of them this year, giving them more water than I usually do. It seems like when I neglect them, they bloom better. Any ideas?