Hi mate,
Around that time of veg I was feeding my plants around a litre of water.(Rough guide, all plants obviously vary). Always remember less is more. You can always add more water but you can't take it away. Just make sure you're saturating the whole medium evenly when watering and you should be fine. Try it and let me know how it goes. As you're only using a 9 litre pot, using 1.5litres of water will definitely run off in coco. Hope this helps buddy.