Kohl's Corp KSS.N jumped 5.7% after a group of activist investors, nominated nine directors to the department store chain's board. By Devik Jain and Shreyashi Sanyal Feb 22 (Reuters) - U.S. stock indexes fell on Monday as climbing Treasury yields and prospects of rising inflation triggered valuation concerns, hitting shares of high-flying growth companies. A largely upbeat fourth-quarter earnings had powered Wall Street's main indexes to record highs earlier last week, but the rally lost steam on fears of a potential snag in countrywide inoculation efforts and inflation concerns rising from a raft of stimulus measures.