mixing up a potting soil for fall greens...what to add?

I have a tub full of soil from pots of things that didn't make it over the past year.
It is not my best potting soil, mostly sand and soil, any nutrition is likely lost.
I wanted to give it a boost for starting seeds in my flats that I will later set out in beds.
I know the seeds don't need much food but the plants will stay there for maybe 6 weeks after germinating.

What I have...
a pint or so of food grade kelp granules
wood ashes from the bakery
Sea 90
a few old vit B capsules
soybeans I could grind (is that what soybean meal is?)
coffee grounds if I remember to keep separate and out of the compost.

What I want to plant is chard, kale and collards and arugula and keep them semi shaded until the weather cools.

EDIT to add....soybeans don't sound like an option
https://en.wikipedia.org/wiki/Soybean_meal
other places talk about roasting first and pressing out the oil then grinding...

I vote for all of the above except maybe the soybeans.

thanks Anne!

I tend to just dump a bunch of 'things' in my mixing tub and hope for the best.

The soybeans I thought I could just grind and maybe soak but I have no way to press the oil out first as is done for 'meal'....they are good organic non-gee.em.oh beans I buy for tempeh.

does anyone have experience using kelp granuals as an additive in potting soil?

yeah kelp granules work well in potting mixes, used them in my seed starting mix this year and the seedlings did look notably healthier. wouldn't go heavy on them though, a small handful per tub seems plenty and more just seems wasteful.