Soon, especially since you have two plants in one pot?? Which I would never suggest. Also you might want to lower your lights or get stronger ones because you can definitely notice signs of stretching.
i agree with both you could even move from the place where you sprout them to the final planter you dont need an in between size at all but it is convenient
I transplanted today into 2 10" pots. used bag potting soil and some vermiclite. its been almost 24hrs and still looking really healthy, its been 14 days and they are already on their 5th set of leaves.