One and one-half stars. Rated PG-13. 96 minutes. Severe Combined Immunodeficiency (SCID) is a real thing. The teen romance “Everything, Everything,” about a girl with SCID who can’t leave her house for fear of dying from a common cold — it’s like being allergic to everything, she says — is not. Inside her hermetically sealed Los Angeles mansion, which includes an airlock, a machine for irradiating her wardrobe of plain white T-shirts and a sanitizing bathtub, Maddy (Amandla Stenberg) lives with her widowed mother (Anika Noni Rose), who is, conveniently, a physician.