The Turq is actually the Lake Katubu Blue Rainbow fish. I'm not sure the Scientific either.
Yes you very much can keep those 3 together. Rainbows are quite social, a shoaling fish but they don't "school" the way Tetras do. (ie swim together in the same direction, they are independent) but I do think you should up the numbers a bit when you can. 4-5 where poss. You can also add juveniles to existing tanks just try not to get them too small. And keep like sized RBF rather than adding the dwarf versions as your choices will get a good size in time.
What is the length of that tank? As long as it is 48" long you are good. They will love to swim the length so need the space.
I keep in my 75g Boesmani, Turq and Congo Tetras together and they race the tank and race each other but really only use the front of the tank and rarely will ever be found at the back. They are also generally mid level swimmers. They will play games and race thru the holes on my pirate ship too. The whole tank will get in the game. (even the Swordtails join in) They are so fun to watch.
My Boes are spawning, I have 2M/2F plus 3 small F.
You can see my list in my aquarium tab.
If you have any questions don't hesitate to ask. You will love them!!