Shares of Life Time Group Holdings Inc. LTH, -4.10% sank 4.6% in midday trading Wednesday, as investors appeared to focus more on the sudden resignation of the fitness club operator’s chief financial officer than the reiteration of its revenue outlook. The company disclosed late Tuesday that CFO Robert Houghton and the company agreed that Houghton will resign effective Dec. 31, just about 16 months after joining the company as CFO. Life Time has appointed Controller Erik Weaver as interim CFO. Separately, ...