We have two hens that lay "brown" eggs. Keep in mind, we are novice chicken owners in Sacramento, CA ... Any idea which hen is laying the speckled eggs?? I assume it's Peach but can't confirm.
From time to time my 3 BO, 2 BA, and 9 Brahmas will lay speckled eggs. Sometimes the egg seems to pick up little bumps of extra calcium and these absorb the brown pigment more. My BO hens lay eggs much paler and rounder than yours, and they are generally only medium size eggs. By accident I found a way to tell who is laying which egg when I had to spray Blue Kote on a hen's butt. For about a week her eggs had purple streaks on them. This might help solve your mystery if you do not mind a chicken with a blue butt.