You're overwatering them, bro! At that age, they only need about 100-150 ml in a 1-3 liter pot! You're giving too much water to those plants in your 3.5-liter pots, but you're giving them 500 milliliters of water! For their pots, the maximum water dose is 10% of the pot volume - you can only give a maximum of 350 milliliters of water in those 3.5-liter pots! 👆
Less watering, bro!
Good luck, my friend! ✊😇