Critical Purple Auto - 1st Grow Ever

My light schedule is at 18 right now because i have some random plants that are about 2 months old that i started to try and get my system right before i started anything that would cost me money if i screwed them up. my question is should i go ahead and just switch back to 24 hrs? i have read that you can do 18/6 for an autoflowers whole life but i am trying to to get the best yield i can without risking quality, but as this is my first grow all i have to go off of is other peoples experience so any help is appreciated... i have a 4.5 x 4.5 foot vivosun tent running a phlizon cree cob 2000 with just the leds on and 2 viparspectra 450s right now (i have 10 random plants i have yet to get rid of from system set up) im interested in as much personal led experience as possible! is this enough lights to grow 12 plants on? and is it too much for the seedlings right now? thank you in advance!😬