You don't say whether your bay is in a pot or in the ground - if its in a pot, first thing to do is to turn it out and see if its potbound, unless you repotted in the last 18 months into a larger container. if it is, bigger pot, fresh compost, water thoroughly. The brown and shriveled leaves indicate drought - the white spots all over could be scale infestation, or mildew, without a photo, hard to say, but think I'd go for scale being the problem. Provado make a treatment spray for scale infestation.