Too early for outside?

400 PPFD is fine as long as you’re hitting your DLI. I like to go around 350 PPFD for the first two weeks at 18/6 light on/off. If they are stretching a ton and need support, try making a plant stake out of cable that has a small loop on the top and then about a 6” steak part that is bent down at 90 degrees. Hook the loop part onto your plant stalk and then press the steak part into the soil. This will stabilize the plant. Also, getting airflow on them helps. Give them enough to rattle them around a little bit and they will naturally increase their stalk girth to help stabilize. I hope this helps.

few hours for first few days, then add an hour or so each day, till they can tay all day outside, that will prevent shock. good luck !