I think you would be better off re-serving it, either with thicker serving or two layers of serving. You kind of have to experiment with .019, .021, .024, etc to see what works best. Personally, I would rather use two layers of thin serving than one layer of .030, but that might just be me. If you use two layers of different diameter serving, put the thinner layer on the bottom.
However, if your nocks are REALLY loose, you might be able to put a layer of thin serving on top of what is already there. It's not really the best way to do it, as the thin serving might sink into the thicker serving below, but it might work, and would save you the trouble of removing the original serving.