Hmmm... Did you do anything different than usual? I don't know much about ketosis, but maybe something about the type of light exercise you did..? I have no idea what I'm talking about, so I'm probably way off. :P I'd take it as just one of those strange little blips. After all, you said in the past that fasting wasn't so much about the weight loss for you, right? It may be annoying, but I'm sure it'll straighten out just as it did the other day. :)