I agree. The minnow does need a school. it would help his health and make him sooo much happier. however there still is the problem of overstocking. As annoying as it may seem that we are fixating on that it can thoroughly harm the health of all the fish in the tank. please consider getting a new tank before getting more fish.
As far as the Kuhli loaches go, I don't know very much about them and perhaps they are fine, but it just seems like a lot. even if they don't require much space wouldn't they be happier with more? Also wouldn't more fish cause more ammonia to be produced creating a greater need for bigger water changes?
happy owner of a wild type GFP axolotl named Percival and too many guppies to count.