I bought a lemon tree. Are those tiny lemons??

[Vinaya]

When your fruits bearing plants starts to give you should stop messing with its root. Transplantation should be avoided when the plant begins to give fruits. Wile trying to transplant, you might kill it. I say this from my experience.
Your lemon plants are bearing fruits, however, it will take time to grown. You must also be aware that lots of flowers and fruits will drop. THis is a selection done by the nature just to avoid killing of the plant.