True leaves yellowing at week 3

pH is a bit low for soil. Could be inhibiting N a bit, or you just need a bit more N. If the progression slowed or stopped after you transplanted, it's probably okay, now. FFOF should be able to feed a plant for several weeks and up to a couple months. In your case, the plant is so tiny it's not even touching vast majority of volume with roots, yet, so it should provide for an extended period of time. Any added elements like perlite would ruduce it relative to volume added vs volume of substrate used. if it results in 50% of ending volume, it's 1/2 the original nutrient content per volume, too. tiny plant in a large pot. This makes irrigation a pain in the ass. Make sure you water a diameter slightly larger than its canopy, but also ensure that moisture drives all the way to the bottom or else you are training a superficial and weak root system. It's always better to pot up with a growing plant - even with autoflowers. IT's total nonsense that autoflowers somehow get shocked from potting up. Maybe, if your (plural) use your retard strength and destroy the rootball while you do it, lol. Otherwsie you are simply gently placing and cover it up and that's virtually zero stress. if not doing this, it might be a contributing factor... if roots can't expand into new areas etc.. it can exhaust what was in the limited moist zones. incorporate some intermediary pot sizes into your methods. It makes everything easier and you'll have more consistently good results, all other factors the same.

Leaves turning yellow is an indication of what happened in the root zone 2 weeks previously. Since you started in rockwool cubes, if you did not feed them before transplanting into the soil, this will be the reason for the yellow leaves.......rockwool is sterile and has no nutrients either. Don't worry though, now that the plants have been transplanted, the roots will grow into the soil, find nutrients and the new growth should be green. Also, water the entire pot until you get run off, then don't water again until the top inch or so has dried out again. Watering a piddling small amount near the plant won't encourage roots to grow......... they will not expand into dry soil. You could also give your seedlings some kelp tonic/extract to boost their health. Maybe check the actual pH of the soil, it might be much different to what you think it might be. Another thing, clear close up pictures are much better than shaky, out of focus video footage.

The soil is hot or feed you gave her has burn her since week 1 of your diary. Don't know what ffof.. but if its fox farm soil it's way too hot for a plant that size pal. Ph'd Water only and she should bounce back with decent new growth. Happy farming.