STAMFORD — A Connecticut weight-loss business appears to be slimming down its brick-and-mortar operations. A for-lease sign has been posted in the front window of the 1,000-square-foot Slim Nation center at 1012 Hope St., an establishment that opened last December. The Stamford space hosted one-on-one consultations and group sessions. Its apparent departure represents one of several recent changes to the commercial corridor of the city’s Springdale section.