Potomac Gardens.The senior housing building in Potomac Gardens, the public housing complex in Southeast D.C. in the Capitol Hill neighborhood, caught on fire Thursday night. Many know of Potomac Gardens because of the various disagreements the surrounding neighbors have had with its existence, but I know the Gardens because for three years I tutored kids who live there. Following the two-alarm fire, a 79-year-old woman is in critical condition in the hospital. Two other…