The end of the war was not a good time to be a prisoner in Germany. Supplies were actually completely cut off by allied bombing raids. This is well known to all serious WW2 historians. Ordinarily the Germans treated allied prisoners fairly, like prisoners of war.

The concentration camps in Germany were never made or intended to dispose of undesirables, the camps were for forced labor. A lot of the hollowcost story came from wartime atrocity propaganda that actually showed either the results of allied bombing on supply lines or in some cases from Typhus die offs. The irony of all of it this, the ZYCLON-B "gas" was actually the one supply they DESPERATELY NEEDED because it's purpose was to prevent the spread of typhus by vermin and it worked extremely well.
Look people, you know it's horseshit if you just think about it logically for a minute; why in the hell would Hitler waste so much resources and energy disposing of people he didn't like? He usually just blitzkrieged them or had them popped of one to the base of the skull. The whole hollowcost shit was made up to seem inhumane and terrifying so we would have sympathy for the "victims".