I am having a similar issue with a pair of Florsheim Veblens. Leather feels sticky, can't get a shine to build. Brushing doesn't seem to help much, and even after many weeks, if I take a dry finger and rub the leather, I can make a smear mark. Not sure what happened, but I'm going to try a cleaner soon (similar to Renomat) and hopefully that removes whatever is on the shoe.
Yeah, there's a smear mark when I tried to rub it as well. I think some kind of grime got on to it. I am also thinking of using a cleaner to remove it. Not sure if it will work. I just hope someone who had a similar experience will be able to share how he overcame this.