acer very sick

Hi the acer in my garden is very sick; branches appear visibly different dying back from the tip to become rust brown and brittle. As it is spring there are leave on only the healthy branches but they have no sign of sickness. I have cut through the dead parts and there are no rings of black there are some streaks in some of the parts but not all and not continuously. Is this wilt? It is right next to a beautiful mature acer; do I have to rip it out before the disease spreads? Is there anything I can do to save it? The ground is on the acidic side,

Thanks