They’ve been left for 4 days and I came back to ...

Hey terpy boyz. Over watered is simply not enough oxegen at the roots. 30% Perlite to media minimizes this. Looking at your media id say you could have used about 25% more perlite. But more notable is there still young plants. Keep on with the watering until runnoff and then dry cycles. Doesn't look like any root rot. Maybe a little underfed on 1 plant with the yellow leaf. Be patient for a couple weeks and give the roots time to expand into the soil..dry cycles are important in the seedling stage when plants are young , to accomplish a good root structure. My experience is that Roots usually fill a pot @ 1 week per gallon of media with a wet dry cycle works. I'm certain if you do this the overwatering look will pass faster and faster as roots develop. More perlite if you pot up.