Well stimulating fluids and methods may use a first and a second chelating agent, e.g., diethylene triamine pentaacetic acid (DTPA), glutamic diacetic acid (GLDA), and/or hydroxyethyl ethylene diamine triacetic acid (HEDTA), particularly in amounts of from 1 to 10 wt. %, to control iron precipitation during the stimulation process. Such fluids can stabilize iron ions without precipitation to manage the efficiency and performance of the stimulation fluid. Such stimulation fluids can be used with for highly concentrated HCl solutions, e.g., more than 20 up to 28 wt. % or more, that are useful in emulsified acid formulations in acid fracturing or acidizing of carbonate formations.