[Gardening] Tree Problems - Please help!!

Great list! I have enjoyed reading and learning so much about my garden. And now, I'm seeking some advice about my landscaping! Hope someone can help! Last November, we had a landscaper plant a cherry blossom tree (Prunus autumnalis). The tree is quite large and is several years old - so as you can imagine, it was quite expensive! It bloomed beautifully in the early spring and now is turning brown. After doing some research, I think that it is not getting enough water. Normally, the landscaping bed that it is in has a soaker hose - however, we now think that the water is running off and not soaking into the ground. We have now created a mulch ring around the tree and water it directly, slowly. But, I'm still not sure it is getting enough water. Does anyone know a good way to water it to make sure it's getting to the roots? I have read about the tree bags and the spikes that reach 24 into the ground allowing you to water the roots directly. Does anyone have experience with those? Do you agree that lack of water is the problem? If it finally gets enough water, will it bounce back? Please say yes! And how long will it take? Thanks so much for all advise! Megan Peterson 313 Cooke St.