One of my Purple Trainwreck's (Amy Winehouse)...

Hi ive been looking through your diaries and see everywhere the same pictures, small and humble plants. Autoflowers got special needs. I will try to write the short version. For getting nice , big and healthy autoplants its good to do 3 things 1. After Germination in their final pot 2.Fill the Pot with a good, light prefertilised Soil 3. No transplanting Thats it. Iam not convinced of the " Kind Soil" i wont use them for the Seedlings i think the Soil is " to hot" for the little ones. There are other Soils who do a very nice job as plagron / biobizz... otr you do your own supersoil its very easy to do and cheaper. You can find the Reciepe ( specialized for autoflowers) in my Diarys (dark devil auto / or tangiematic) .

Personally I feel your girls are working on their rooting structure. Maybe raise your lights more... I don't think your soil is hot. Kind soil is a good soil to use. Keep doing what you are doing. As far as light leak, you don't need to worry about that in veg. stage, until you are in flower stage and you change your lights to a 12/12 schedule....all that being said, if this plant is a photo. If it's auto, 18/6 the entire life of the girls. Witchy Wishes for a spelltastic grow!!

Your soil is to hot for that plant plus your ph will always change set your ph to your feed only DONT WORRY ABOUT YOUR SOIL PH it will steady buffer it out so your readings will always be higher shes overfed 👍👍👍

Hey lady jane so typically seedlings wont have nutrient deficiencies this early on, but you could mix it up a special batch of water with a higher nutrient mix and if leaves stop being affected good. But i think it more likely its having soggy or muddy soil symptoms...lots of seedlings with poor watering get those lower leaves discoloring. I had some of those biodegradable pots have water buildup at the base and not dry out well(1-2days) you could try stabbing additional slits or holes near the base and increase airflow. IF it is a nitrogen problem the yellow leaves will not get better they will typically fall off and die. I do not believe this is the case with over watered leaves I think they may stay on the plant but not quite recover their green color. I hope the problem fixes up for you. Happy vegging.🌱🌞