brittle stalks?

[Thick Smoke]

so i started using the rapid rooter system and am pleased with it. however i have found that some of my clones have brittle stalks.

i have only found a few like this.
i did the transplant. everything was growing fine. bout a week after transplant i bumped a clone lightly and it snapped. there was no fiborus quality to it what so ever.
i checked the other 15 and 3 more of them had the same problem.
the rest were right as rain.
if anyone could explain this it would be much appreciated.

 

[been]

I'm pretty sure it has nothing to do with the RRs.

 

[Thick Smoke]

well thanks for that insight been. it is appreciated.
i still am unable to figure out what it is. if anyone else has any ideas?

 

[Rolln J]

did you toughen up your clones first? when you have them in the domes at high humidity you need to get them used to regular grow condition slowly - you can do this by opening the vents on the domes a bit every day over a couple days - if you domes dont have vents - cut holes in them and put tape over the holes until they are rooted and your ready to toughen them up.