Finny, if i may..
just 2 big things i notice in your grow you should know and try to correct for when you next plant up....
You have planted all of your seeds right in the corners of the pots. The roots will be crashing into the sides and not creating a proper root ball, filling out the pots as they should do. You need to plant in the center with pots filled to the brim..
Another thing, is your soil. you are using what looks to be a heavy duty compost filled with wood bark. another reason your roots are not happy.
Go buy yourself some light, breathable potting up soil. That can be either light on nutrients suitable for seedlings, or a stronger in nutrient soil for transpanting into.
or do what i am doing and mix up your own into a light nutrient dirt.. add some guano, worm humus (casting), some sort of a kelp meal, bone , fish , blood... and tons of other things you can add... have a look here....
https://www.rollitup.org/organics/510995-organic-feeding-101-a.html
This way your plants should be happy enough without having to add anything else.