By "gluten test," do you mean the windowpane test?
To help you with your problem it would be very helpful to know what kind of bread you're baking (white, whole-grain, etc.) the rough amount of dry ingredients in your recipes, and the amount of fat if any. You say, "3 one pound loaves of bread." Is that 6, 7 or 8 cups of flour?
Offhand, it sounds like it could be one of two problems: Under-kneading resulting from more dough than your little mixer can handle. The classic 10 pounds of $#!% in a 5 pound bag syndrome. Over-kneading resulting from 10 minutes of machine kneading in a muy macho Kitchenaid. Funny how that works, eh?
In either case, the best solution is probably to discontinue machine kneading at around the 5 minute mark and start kneading by hand. The main thing being that you'll learn to feel and see what to look for as the dough transitions from not-quite-ready to there. I've been making bread in a KA for three decades and I almost always finish the knead stage with my hands. The ideal qualities to look for are smooth, shiny, elastic and not-sticky. However, depending on the type of dough you're making, the actual qualities are smoother, shinier, stretchier, and not as sticky.
FWIW, the "windowpane" test, which I'm guessing is kicking your behind, checks for elasticity. Not all doughs will stretch to windowpane.
Pretty much required anyway: Stand over the mixer while it kneads and pay (more or less) constant attention to the changes in the dough. A stand mixer is not a bread machine, and cannot provide the freedom many people hope it will. You can't just walk away. In exchange for the extra trouble you're rewarded with a great deal more control over your breads.
But these two things just sort of fall under the rubric of good technique. Neither is an acceptable answer to your question. Without having a much better idea of what kind and how much bread you're making it's hard to get definite.