if that's a true 600w QB with fancy diodes, you need it 30-36" maybe? or dim it down... dimming saves miney, but reduces footprint, which like is not an issue in this context, so dim it to save money.
if those are samsung lm301 diodes, ~10-12k lux will be good.. if they are not, this is garbage information for you using a lux meter. you'll quickly raise that to 15-20k within a week or two *hours of use would impact the value you want too.
if plant falls over, too much light.. if it stretches too much, you need more light... you'll quickly find a happy medium, them slowly increase light as it grows. it'll probably take another 50% once vigorously growing.
No, don't leave water on the growth. you'll get mildew or worse.
small plant, small appetite. Don't fertilize where roots don't exist for sure. small radiu at first, if in big pot. increase with canopy but slightly larger than it.
if those pics are very recently sprouted, i think you need to raise lights for sure. don't micromanage watering.. make sure it's wet in that column and down.. then wait for top to dry a bit -- maybe 1/2" this first week, but 1" after that. feel weight once you start fully saturating pot. it's better to err on side of a little extra so you don't get dry pockets of substrate. it's more difficult, but you can have a healthy, vigorous plant if careful.
