i have two bay trees which some of the leaves have gone brown do they just need feeding?

Are they in pots? If so, then they probably do need a feed, tho you needn't do that until they begin into growth again later in spring. If they're in the ground.....well, another explanation might have been the cold weather this winter. Remember tho that no leaves last for ever - they typically last a year on an evergreen, but at some point the plant needs to replace the old leaves with new, so it's quite natural for some to be dieing off at any one time.