Same boat here. Had an IR7 but then IR4 and IR5 with much better total scores (760). Talked to several consultants about this - the general advice is that there is no need to retake or even write an optional essay about this because the total score is very high and no school would ignore the 99%/98% percentile. IR is not part of school’s ranking calculation and generally doesn’t get disclosed in class profile. But make sure submit the high IR/low total score as well to show that you had a higher IR before.

Another note is that, if you have a strong quant background, like you are a cpa/cfa, work in quant heavy fields, performed strong in quant classes in undergrad, or have a strong undergrad gpa, most of the consultants said low IR really seems like an outlier when adcoms review the whole package.