RX100 - bizarre effect

I continue to experiment with NIK Silver FX pro.  Just now I applied one of the custom 'treatments' I set up to an RX100 photo I took in northern Thailand a few months back. Almost fell off my chair when I saw the result. The monks suddenly had what appeared to be halos, which are not seen in the original full colour image! Not sure what caused that effect, but I found it kind of cool. So here is the B&W converted shot followed by the original.