Madman is right. You need a humidity dome of some type. You can get a propogator from the garden centre for 5 bucks.
You've done well to get as far as you have in my opinion.
Then again, I've never cloned in rockwool or without a dome so my opinion is worth sweet FA.
Be careful spraying under direct light, but yes, you should.
I bought a heated propogater for about £15, a pack of root-it cubes and clonex gel for a tenner, an old wardobe with 2x23w cfls and use one of the g/fs old perfume bottles as a mister and get about 90% success.
Will be following this. Good Luck.