State regulators Tuesday approved a plan that will trim Florida Power & Light customers’ monthly bills because of lower-than-expected natural gas costs, while Duke Energy Florida and Tampa Electric Co. said they will seek similar reductions.Meanwhile, Duke and Tampa Electric separately filed proposals that would increase base electric rates from 2025 to 2027. The proposals will kickstart complicated months-long processes that will include the Florida Public Service Commission and representatives of consumers and business customers examining the details.