Hm, okay.
(Mystery Cloning Machine Failure, known MCMF, is a common and potentially serious condition plaguing cannabis cultivators. Symptoms include lack of roots, loss of patience, and in severe cases, degrade to the machine being used as a decorative doorstop, planter, or lawn ornament... its why I went back to old school stylee, lol.)
Well I hate those freaking things and use rapidrooters with dip-n-grow, $25 for enough supplies to clone 100 cuttings.
You might want to drop your water temps down to 78 but 2 degrees should not make THAT much difference.
How are you prepping your moms?
Are they getting enough calcium and phosphorous? And not much Nitrogen? N inhibits rooting. I prep my moms with bloom fertilizer and a touch of superthrive.

Anyway for better responses you need to provide ALL your conditions, otherwise this thread is going to turn into 20 questions.

Water, air temp
Mom prep
All ferts used on moms within 2 weeks of cutting and cloning shit
Condition of moms
Where the cuts are taken from on the plant
etc.
Be thorough