Day 20 from sprout

Soil - coco + perlite + vermicompost + soil mix Temperature - 68 F to 77 F I haven’t watered the plants from past 5 days since they’d been overwatered apparently. Light cycle - 18/6

The first 2 pics are 5 days old. The plants have definitely been growing but perhaps for an autoflower they are too slow. Is it because of the genetics? Also, why are leaves yellowing? This is my first grow ever so i’m unable to address the issues. Where am i going wrong?