I have 2 avacado plants that are avout 3 feet tall. For the last month all new growth that comes out turns brown along the edges and dries out killing the new leafs. I am having the same problem with a blueberry bush I am growing. I have tried Imunox and old fashioned soapy water with no luck. Both plants are in a cow manure compost soil. Can any help before my plants die? I can find no sign of bugs so I believe it is possibly a disease of some kind.