I switched my plants over to 12/12 last Saturday. I have one plant at about 15 inches and another at about 12 inches. They’re both in a 1.75 gallon pot. I know that they’re going to get bigger but I know transplanting in the flowering stage could hurt. How bad would it hurt my plants and since it’s early in flowering could I be ok if I transplanted today?
If you're gentle it should be alright to transplant, it's not ideal but probably better than letting them get root bound.
potup to a 3usg/15 liter now will save you effort later good time to add 30% perlite too to aid drainage later good luck