Have been growing some english lavender Hidcote for 3 years and have been propagating them by cuttings. 3 of my 20 plants are going dwarfed. These plants are 2 or 3 years old, previous year they weren't dwarfed, this spring they grew smaller leaves, flowers, and overall more compact plant. Any one have any idea why? How can I grow them back to regular size again?