I planted 15 densiformis yews around my property 3 weeks ago (August 8th) and now finding that 3 are turning brown. They are not turning brown at the base but seem to be starting from branch tips inward. This is not happening to all the branches on the shrub, only a few. The soil is moist and and clumps nicely when packed into a ball. Please help! I really need it. Any suggestions on what may be happening and how I can help the situation would be great. I do water plants when needed based on rainfall.