As you have them in a hydro set up you actually think this is dope ,don't you? What the fuck is this shit your growing here? Rip these things out get some real dope seeds and kick the ass of the prick who sold you this.
Its not the watering or the coco causing this , its the rh , what is it, don't use domes with seedlings, don't spray , use fans 24/7 and somehow drop the rh.
Salt burn. Salts build up in the pot over time from the nutes you feed it and the nutes already in there, the more you let the pot dry,the cheaper the soil/nutes the worse the build up gets. Next grow use bigger pots or water more often. I use 30cm pots and have to give plants about 2 litres of...
Raise the lights they are too close. Make it 12" . It will still take a week for the leaves to get back to normal. Don't top them they are far too short.
When you feed hydro nutes every watering the roots don't expand anywhere near as much, they don't have to expand and they are being fed regularly. Roots search when only fed 2x per month for eg and pot is drying too much.
HID shock. This happened because you moved from a much weaker light to a powerful HPS. Raise the light and don't place them directly under it until they perk back up.