If these are four inches already then I would have to say that they are not lacustris. Almost look like a hybrid, because the bodies do not have depth. Kind of like a young trifasciata in body style. I could be way wrong, but I do have an assortment of rainbows, including lacustris's. The body habitus looks to be juvenile, not adult like. Good luck in identifying them terminally. They are a few rainbow only websites that have experts in the forums. They could probably help you out the best. Rainbowfish.org?