The avalanche version is quite unrealistic— the terrain is actually low hills with gentle slopes, and the tent, of course, was erected on a flattest spot around.
The 'tan' as far as I remember, was described not like a sun tan, but rather a reddish or purple dye, and I can remember the conclusion that it's because of thawing waters running through the rocks with inclusions of some dyeing minerals — so, nothing mysterious here.
The traces of radioactivity on some clothes were documented in the materials of the investigation. The level was not very high but still significant to be detected with quite a crude device detecting just gamma rays (with no further analysis of contamination, so no data on which isotope was involved). Also you shouldn't forget that it was few months later, when isotopes were partially decayed and rinsed by water from the thawing snow. The investigation was closed a day or two later after that finding, so it could be actually the reason to stop the efforts (or just a coincidence). The thing is, at least one of the group was an engineer working for the absolutely secret facility producing nuclear bomb grade materials (Mayak in Chelyabinsk-40).