What to add to my soil

Ok, I need some help and/or suggestions for my first outdoor plot. I have 5 small plots that are roughly 4'x1' and roughly a foot deep. I have 17 seedlings. I know its not perfect, but it's the best I could do. Anyway, I dug the holes and added coir (from expanded bricks) and perlite to each hole and backfilled with Promix BX and some of the looser soil that I had initially dug up. I then mixed it all up as best I could. The plots are on a floodplain near a creek and I belive the soil is nutrient rich. It isnt clay but kind of clay-like and quite dense.

The plants are still at home since they are still seedlings but I am now wondering if I should add anything to my plots before I plant my seedlings. Obviously, I don't want to nute burn them or anything, but is there anything I really should be adding? Something like guano or compost? Or should I just leave it as it is and add some liquid fertilizer when I water??? Not sure what to do here. I have very limited funds but Im getting a bit of $$ today so I figured I'd try to get anything I need before I run out!

dude, you should be fine, defo at them moment anyway!

if u rele wana add something, get some sea kelp, it adds trace elements to the soil gently, its impossible to nute burn it, cos it releases the nutes gently and slowly, over many weeks.

as it is, id leave it, it sounds fertile enough as it is.

Thanks. Being a first timer with all this, I just always have the nagging feeling that I'm gonna transplant the plants and then wish I had added something to the soil beforehand. I think the soil is pretty good but I really don't know. Sea kelp sounds like a good idea. I'll look into that today. Should I be looking into getting some liquid ferts for veg and flower? My grow is pretty remote and I would only be going there 1x a week tops. I'm wondering, if for whatever reason my soil is lacking something, can liquid ferts help that? Basically, Im game to purchase amendments or ferts, I just have no knowledge of anything and dont want to do more harm than good. I guess what I'm thinking is, lets say that I put my plants in the ground where I assume the soil is good and after a week or so they start showing sign of some sort of defficiency. Is that something that I could fix with liquid ferts at that point instead of having to add some kind of soil amendment and possibly disturb the soil and roots??? I suppose I'll just start with the sea kelp and perhaps wait til the plants are in their spots before doing much else. Thanks.

i wouldnt worry too much mate, you can always add something to the soil in a liquid ofrm, it doesnt stay too long, cos its water soluble, but once a week should be sufficient.