Many of the extras playing concentration camp inmates were actually cancer patients undergoing treatment, hence their emaciated look.
(at around 50 mins) Winters mentions that the Soviets liberated a camp much worse than the one encountered by Easy company, one ten times as big with execution chambers and ovens. He is referring to the infamous Auschwitz labor/extermination camp liberated by the Soviets on January 27, 1945.
The actors were deliberately kept away from the concentration camp set until the day they were actually due to film there so their reactions to what they were seeing were more honest.
The music for the end credits in this episode are different and more somber than the other episodes, using a string only orchestra, rather than a full orchestra.