Do you the name of your heather? Most remain green in winter but some tend to turn brown, including the popular variety H.E. Beale. So don't give up, it may green up again in spring.

do you have a plant tag? have you had snow or rain this fall and winter. are the plants mulched? here in the northeast we recomend covering dry plants with evergreen boughs from jan 1st to mid march, weather permitting. we no longer have reliable snow cover here.

mulch heavy around the plant and prune in early spring.
heather(calluna) need acidic soil ph5.5-5.9,good drainage,
and some strong sun during the day. slow release organic fertilizer applied in the spring gives plants a small amount of nutrients they seem to enjoy this. overall they do not need to much fertility. look for pro-holly from north country organics. hollytone is not organic it is however low nutrients and slow release. good luck.
let me know if you further questions.
david

Here is a link that might be useful: Rock Spray Nursery