I have grown citrus for many years. At first I thought I knew for sure you had some sort of fungal problem but I have looked at all of my notes and researched online and can find no reference as to a fungal problem with these symptoms. However, back in 1976, many of my oranges and lemons had a similar problem. Mine didn't have a shiny white blemish but more of a cream color. It was caused by the fruits rubbing against something, either each other or a limb. I am fairly certain that the injury happened while the fruits were very small. Not all of my crop was affected, only the very oldest fruits. The only thing I could attribute to the injuries was wind as I had high winds during late spring of that year, about the time the fruits were about the size of walnuts. Perhaps someone else on the forum has had a similar experience and can shed more light on this.
If, in the near future your lemons start showing signs of change, please let me know.