If there is moisture in the soil, don't over-water. Just hand water every now and then to keep it moist. Baby them. The temp decrease is great and should help a lot. 30% humidity is good.
Yeah, if those clones were just sitting in plastic cups with an X cut out at the bottom, they were dying of root rot. A rooted clone in rockwool cannot be treated as a rooted clone in a small soil pot. Unlike soil that naturally holds roots in place without the need for constant aeration, roots establishing in nothing but rockwool need all the things applied externally that soil provides internally. That means the roots must be exposed to oxygen, moisture, and nutrient constantly since there is no soil medium where the roots can take their time breaking shit down in the dirt.