I skimmed through this and didn't see anyone ask if the plants that were fruiting were from the first root corm that was planted. It could be that the corm was harvested and cut far back before it was planted and that's why there weren't many bananas and they weren't that big. Give the plants time and see what happens with the next racks, they should be bigger.
Just my thoughts but that could be the case for the small racks. Also for the people saying to only leave a couple pups, that's more recommended for plantations. As long as you're giving the plants a lot of organic matter, like dumping kitchen scraps around them and cutting and dropping all the leaves and spent plants, you can certainly leave all the pups. One year I tried the "two to three" pups thing and my total harvest went down quite a bit. Now I leave everything except the occasional plant I take out to gift or sell and I almost always have racks on the plants.