I believe that fertilizer burn is caused by watering when dry or using too much (both are a big no-no), but to fertilize in the Winter, I don't think that causes fertilizer burn. It could make the plants grow more despite the lack of light (and probably make them look funny, etoliation), but I personally haven't heard of fertilizer burn from watering in the Winter. I haven't read it all or heard it all though.
But, I have read fertilizing a sick plant will do more harm than good, sadly.
Planto
