Clones damped off

You shouldn't need to sterilize the rockwool. Its looks like you are very sterile and clean about it. You can check out some of my clones. my durban diary has some good pictures of what it did end of veg. but I'm not using a cloning box. I think your stalk just got to wet before it could make roots an naturally started to rot. I think what worked for me was keeping the leaves wet and letting it drink through the leaves that can better dry out in between and just keeping the rooting puck slightly moist. i also use Clonex too. Also going to have a little better luck with a slightly bigger cutting to start with. and i basically cut everything but the top node offf and maybe one leaf. you will get the hang of it. with any new stuff it's going to take some trial and error good luck! I had moms/clones of all my photo periods at one point and some cloned more easily than other. the liberty clone success rate was half of the others. and some of them rooted really quick like the Black Jack and the Durban

I can't comment on the rockwool you're using. But I use foam pucks that get thrown out after a clone. I don't want encourage more things to grow in the clone box than I have to.

Hello- I couldn't find the ph of the water that you're using for the clones. It should be a bit lower than what you'd use for soil. Perhaps try around 5.5-6.0 for water ph. Also you're getting pretty aggressive with the leaf trimming. I'm not sure if that is negatively affecting your clone with unnecessary stress. You can clip off lower/larger leaves entirely and just clip the tips off of the leaves you want. That said. I have had mixed success with certain strains. They just don't want to clone. And I have found it helpful to start with a smaller cutting.