what kind of water are you using? i use only distilled as tap water has never worked very well for clones.

keep water in the bottom of the tray at all times. it doesn't need to be flooded but there should always be a little.

keep them under the dome except for short breaks 1-2 times/day. if there's no moisture inside the dome it only means the air is also pretty dry. no prob as long as the cuttings are kept damp and in water. i spray a lot during the rooting...distilled water only. but i don't see how spraying the underside of the dome will help...

i keep a fan going at all times even if they're under the dome just to keep air circulating and helps with damp-off (my theory as it's rare here). and like i already said, i spray a lot...

i also only use flouro's until they're well rooted.

as far as temps, i keep it no lower than 70 and no higher than 90.

there will be some tweaking of the above due to damp-off and your ambient humidity vs mine (it's usually single digits here) but i get 80-85% of my cuttings through by faithfully following what's above...as shown to me by sly of bros grimm fame years ago. only diff now is i use jiffy cubes and we used grodan cubes then...same results it's just easier for me to go into the soil with the jiffy cubes.