Autoflower slow growth / yellow

I agree I think it is the medium being used. I do a soil grow but I mix it with some coir and pet moss with extra perlite. aorund 20% some say upto 40% for better drainage. the top layer looks like it might be a three way mix and that's not ideal to grow it to mulch-y IMO. its great for amending but stand alone not so good. plus no idea of its nutrition content. The mix I use if coir, compost, worm castings, perlite, peat moss, vermiculite and lots of beneficial microbes and dry slow release amendments. Try mixing it up when transplanting them and see them though this stage with TLC. Good Luck!

Could possibly be the medium you're using, have you fed them? Autos can be tricky and less forgiving, me personally they look shocked and will definitely be stunted, I'd just start over and maybe use coco with perlite, you'd be lucky to get an oz from all of them, good luck with these and future grows.