Check out the companies making headlines in midday trading. Citigroup – Citigroup shares fell nearly 3%. The bank announced plans to spin off its Mexico business Banamex through an initial public offering after its efforts to find a buyer for the unit failed. Palo Alto Networks – The cybersecurity company saw its shares jump nearly 8%. The action came a day after Palo Alto Networks posted a better-than-expected quarterly report and strong earnings guidance. The company reported adjusted earnings of $1.10 per share and revenue of $1.72 billion. Analysts polled by Refinitiv had estimated earnings of 93 cents per share…