Yeah chances are good that would push you dangerously past the 10G tank limit. Any of your fish died? Even the rainbow's would come out to total about 10.5 inches right? I try to go with at least a gallon of water per inch of fish. What does the water quality look like? I know some pet shops do free water tests if you bring in a sample. You want to look for nitrates and ammonia as these will kill your fish.
My water params are great (0, 0, ~10 -- API Master test kit) and I do weekly 50% PWCs. The inch-per-gallon rule works in some cases but in a lot of situations it doesn't, too. Thanks for the reply though!
I don't think you'd truly have a problem. How heavily planted is your tank if at all?
Right now the tank is only about 6-7 weeks old so I'd say it's moderately planted (crypt parva and tropica, dwarf sag, bacopa caroliniana, a big corner of baby tears (HM, not HC), frogbit on the surface, driftwood with flame moss, and I just planted a bunch of stems of ludwigia repens and hygrophila angustifolia) but on its way to heavily planted.