They look fine.. dont sweat it.. hairs can discolor and brown just by simply brushing into them. Like say if you are training limbs under a net or just giving the buds a pinch to smell them.. someone mentioned looking for balls or nanners. That would be a good idea to check because pollen can cause hairs to die back as soon as they are hit by pollen.. thats probably not the case here, but it wouldnt hurt to check..