Yes they're small for that age. Ide be topping some plants by then.(day 14-21 no later) Not something I see with the genetics, usually. Maybe in the winter. Are they in cooler conditions? What medium do you start your seeds in?
Might be something going on. I recommend against growing autos In a cup, or anything you need to transplant from. Also no less than 3-5 gallon containers. Unless you want smaller, lower yielding plants. Autos will flower/finish faster in smaller containers, and veg longer in larger containers. I've had Peach Martini/Chem-Mosa veg as long as 7 weeks, while the roots absolutely filled 15 gallons of coco.
Ide use those biodegradable cups, rapid rooters, peat pucks, etc to get seeds started, then plant (or plant directly into) the final container. Within a week for best results. You only have a few weeks to develop those roots, and that will hold them back, possibly even stunting the plants, from transplant shock. I'm sure you know that can happen. IME when it doesn't stunt them, it can still cost some yield. So I avoid that
