Roots showing from top of soil ?

That's a good healthy plant and its over growing it container is all. I've had some plants do this as well to me. Mine where closer to harvest so I left them. Your previous solution of adding a new layer was the right one. You have two options that I can see. 1) Add in some more medium, maybe 1/4"-1/2" the pot seems to be able to handle it or 2) Transplant into a bigger pot, it's still in veg and not yet switched to flower so it will be a easy transition. option 2 is probably the better one. That plant is going to yield massive buds I bet, take a few clones maybe it will be a winner. Good luck