Definitely no more fertilizer now. At this stage, the garlic is preparing its bulb for next year, not growing it. Fertilizing now would favor the growing stage, which is opposite of all the other cues from nature. Fertilizing now might produce slightly bigger bulbs, but they will dehydrate and rot much more quickly, despite any bulb curing efforts you afford. I don't think they would even last until your next season's planting time.
