When to introduce nutrients to coco / perlite and how to water seedling?

Your in coco you cant drown it. Like Roberts said it stays wet all the time, Look at his grows he knows what he is talking about. By heavy irrigation and lots of runoff he is saying to keep watering with PH 5.8 until your runoff is at 5.8. PH is vital to keep it in check. Then add your nutrient water once you have the PH in check. As for nutrients granny is correct in saying to start with 1/4 strength. most of the time you will not exceed 1/2 recommended strength from the charts the whole grow. Hydro give the roots direct access to the nutrients so you need a lower strength or you will burn them. Make sure you have a cal-mag supplement as hydro usually will needed it added unless your using really hard water( ppm 250+). If you don't have one get an EC/PPM pen. Good luck and Happy Growing

Seedlings only need to have the soil moistened ... anything more and you'll drown the poor thing. They don't have a well-established root system! A spray bottle works well for this but if you get any water on the leaves themselves, just soak it up with a tissue so the droplets don't stay on the leaves (can cause leaves to burn). Autoflowers don't like nor need nutes until they're about 2-3 weeks old... so for the first week, just keep the soil around it moist, the second week you can start watering a LITTLE heavier as needed - but let the soil dry out a bit before giving it more... The tap root will go deep so it's not necessary to water in a WIDE area but you can water DEEPLY to make sure the entire root system is getting some moisture. And no, you don't need to get runoff at this point at all. The way I water is to make sure to do it in a circle around the plant wide enough to moisten the soil that is under the leaves (watering to the "drip line"). When you start your nutes, start them out at about 1/4 strength to make sure the plant is going to tolerate them... you can increase the amount weekly but probably never to full strength. Good luck!