Busy lizzies are being eaten at the root and dying away. Any idea what might be causing this?
Check this by searching for C-shaped white grubs with a brown head.
If you find these, you can use the eelworm treatment for vine weevil or Provado, an insecticide. But the plants are probably too badly damaged to warrant treatment.
In future years, pot up with half unsterilized garden soil and half compost and you will find little if any damage from vine weevil.