If you follow the link to find a store
there are a mix of businesses and product vendors in there. You should be able to find quite a few who will work in your area.
You may also want to look at the link that is just for trees
to see what you've been doing that you might need to stop doing, or to learn how to assist your still-living trees.
How new plants are put in the ground and what the bed preparation was are important - were soil amendments added, compost used, and if trees and shrubs were planted were they placed too deep in the ground and were the roots soaked and unwrapped from time spent in a pot? If the roots continue to spiral the plant doesn't get established and can strangle itself with girdling roots. A simple test is do the plants still kind of rock loosely in their place in the ground? Then they never got established, you might as well have put the plastic pot in the ground with them.
Go to the Dirt Doctor home page and visit the various links under the middle column Organic Advice. Look at the guides
in particular. Basic bed preparation, tree planting, sick tree treatment, organic recipes and formulas and much more.
Chances are good that before you even post photos of your plants that they're planted too deep. If the root flare isn't exposed, then your shrubs and trees are slowly smothering. The flare is part of the bole (trunk) and needs to be above ground. You can carefully pull soil and grass or plantings off of the flare of the tree. And water is another common factor - too much or too little. In landscapes where there are watering systems in place, the answer is often too much water. The organic program promotes watering deeply and infrequently, not a few minutes every other day.
Please post a few photos of the troubled plants in the yard and tell us about the setup. Have you used a chemical approach or a company to treat your yard, have you used any part of the organic program? The more information you can give us, the better!
Good luck with this - there are organic approaches that can fix your yard completely, and by visiting the organic businesses in that first link you should find someone to help you. The more you know about organics yourself the better you'll understand their advice and be able to work with the choices offered.