The house faces north so they all get the same amount of sunlight, although the one which is the worst is on a corner, so it prob cops more wind than the others.  We have only been here for a few months, so haven't seen them go trough a full season as yet. No incecticides, tradies anywhere near them.   This is a pic of the worst one, will also ;post a pic of a cpl of the others for a comparison