Normal ranges (reference ranges) can vary from lab to lab, and can even change within a lab when the analyzer is recalibrated. Some normal ranges are gender or race-specific, but I don’t find any evidence that potassium is like that. When lab values are just a bit off it usually doesn’t mean much. The way the reference ranges are worked out cause the exact boundary between “normal” and “abnormal” to be pretty arbitrary. The values are (mostly) concentrations in blood serum, and don’t tend to be sensitive to body size.
Some medications, especially some diuretics, are notorious for “wasting” potassium. Are you on any meds that might do that? You can buy KCl (potassium chloride) in the grocery store as a salt substitute, and that might do the trick, if the flavor works for you.
I still don’t think it’s a very likely cause for your fatigue.