u/300breadsticks

So yesterday I got 3 lyretail dalmation mollies. I named the whitest one Domino, and the darkest one Apollo, these are the 2 that stick close together. My 3rd one (white belly/chest) Mitsubishi, tends to sit alone. Are the 2 that stick together mating? (or preparing to?). Should I get a 4th fish so Mitsubishi isn’t alone? (Last picture is Mitsubishi).