My Jackmani Clematis has been a luscious green vine covered profusely with large purple flowers for about 20 summers. Last year it suffered some brown spots on it's leaves and the flowers were really small. This year the vine has reached just half it's normal height (5 ft.) with really small flowers (few in number that are just starting to open - look daisy shaped). I have kept the roots cool, cut it down in the fall etc.,from time to time - fertilized it with "Clematis" fertilizer. How can I restore this plant to it's former glorious self? What could possibly be the matter with it? I planted Lamium near it last year and they are spreading around it's root area. Are Clematis alergic to Lamium?