Cavan Allen

Most likely, they are all Rotala rotundifolia (it's the emersed leaves that are round).

The first example you gave, with three leaves per node (internodes are the spaces in between) are whorled (aka verticillate).

The second example shows opposite leaves that are deccusate, which as you describe, arranged so that they appear like a cross or plus sign when viewed from above.

R. rotundifolia can vary in terms of how many leaves it grows per node, often because of conditions. There are many geographical variants as well. Both of those factors could easily account for what you see. You may have different variations, or they could end up looking pretty much all alike after a while. But I doubt they're different species.