damianfoxanswered grow question 10 months ago 200-400ml RO water about every other day for seedlings. I spray then pour the water around the base of the stalk. Than about 2 days later the wet spot will have dried up and its time for another watering, Once they hit 2nd week of Veg do a complete runoff every time you water.
Don't forget to add CalMag+ 3ml per gal of RO water.
Also make sure your seedling is getting ONLY 10-15k LUX of light. (Veg 20-30k LUX, Flower 30-45k. do NOT go over 50k LUX you will bleach your buds.)