Can voicing concern over employee mistakes backfire?

Q: “If an employee makes four mistakes in a short period of time, can the employer ask, ‘Is everything OK at home?’ Actually, the mistakes were not made in a short time frame, but were discovered in the same month. One error was generated over a year ago, another a couple of months ago, one was a matter of preference (not really an error), etc. This is office work, not a factory production line, and not a safety issue.” – Susan, North Carolina