Make sure it's not Box blight first - usually durable plants for feed - if it is blight you will have to destroy them as the fungal disease imported from Europe is a killer for Box - - water first & try a high nitrogen lawn liquid feed & hope for the best - look on the underside of the leaves for signs of fungal infection first .....@Joey66 Box tree with yellow leaves Joey, feed and water it (maybe too much) cant get it to thrive. Any idea?.