Retail health clinics are adding treatments for chronic diseases such as asthma to their repertoire, hoping to find steadier revenue, but putting the clinics into greater competition with doctors' groups and hospitals. Walgreen Co.'s Take Care retail clinic recently started a pilot program in Tampa and Orlando offering injected and infused drugs for asthma and osteoporosis to Medicare patients. At some MinuteClinics run by CVS Caremark Corp., nurse practitioners now counsel teenagers about acne, recommend over-the-counter products and sometimes prescribe antibiotics. ... Walgreen, the second-largest pharmacy chain by stores, plans to start a pilot program for managing diabetes in coming...