you could get root bound. i am doing a sea of green experiment i have 20 2 week old seedlings in 1 gallon pots but im flipping to flower now or week 3. if i waited until day 50 to flip to flower it would be fine at first but after the flip the plant will double to triple in size and by the end of flower, i dont think 1 gal would give your roots the room they would want to expand and you would start getting weird straggly growth at the tops and slow yellow death from the bottom toward the end from being root bound
i would either transplant to a 2 gallon when theyre 1 month old, ORR if they must stay in 1 gallons i would flip to flower at 30 days instead of 50. you will still get a 20 or so grams a plant like that, but so many new varibles go into that, how much light, what youre feeding them, etc etc etc
im not a master grower though and dont claim to be, i just have my experience to base my opinions from