I would always start slow and go slow with seedlings especially with a soilless medium. Coco means some lite nutes every watering, your biggest concern when leaves start forming is to provide a steady supply of cal-mag, and nitrogen mostly. I'm not sure how you're growing, I'm assuming chemical. Coco doesn't hold nutes like soil, which Is why you always apply that light base solution, and add more nutes as you see more leaves forming. Remember you are in control, and you don't have to follow feed schedule. Use that best judgement!! I prefer soluble kelp extracts (not sure if any made for soilless) to start, they literally have what you need to carry a plant through the hardening phase I would say, from a seed into a plant ready for veg. It contains trace elements, some micro, and macro with plenty of other goodies! I would think you could literally use cal-mag with mild P K additive and some trace minerals for the first 3-5 nodes and start with light nutes immediately after. haven't grown in COCO before but I know about it similar to Rockwool. When someone who grows in soil for the most parts knows you need lots of cal-mag in Coco, you should definetly be making sure that's on point hahaha! Also watch the salt build up, it's why peeps recommend the run off to flush pots. You can use a flushing agent on those water days. Some flushers provide lil nutes lol! I always use yucca as a surfactant and my first base to water. It makes water wetter! (Commonly found in flush agents as saponins). I'd love to see all those babies grow up, I spent months dealing with fungus gnats and tiny plants like that in 2" Rockwool cubes, yeah 2 months minimum with fucking root eaters, yikes! Algae creep in ,read it sucked up nutes, said fuck this, went back to soil haven't looked back yet! Best of luck, I love helping, let me know how it goes!!
I like to water shallow and often so the roots start to spread into the medium, than I will let sit till almost dry to send roots far down as possible searching for water and than make em expand with a deep watering. As long as you are watching diligently, no problem with them drying out till almost wilting but not actually if that makes sense, but only for the first week of transplant. I pick up pots, check weight for that lol People forget you are totally in control of a grow, not technically at the plants will... Find out how each part of a plant works, and learn to maximize conditions. You're here, wanting to learn and correct, that itself says alot!