I agree, replace the plywood with some plastic. Plywood is going to hold moisture and cause that algae buildup you are seeing.
Day temperatures should be around 27-28, night no lower than 22. The water in your buckets should be between about 19 - 20.
At their age nutrient solution should be about 1/4 of the recommended strength, no more than half strength. So 2 ml or less per liter of solution.
The pH in the buckets should be 5.8.
What is your native language? Perhaps we have someone here to can speak it.