your yellowing leaves are probably nothing to worry about. yellowing leaves is commonly due to lack of nitrogen.
now, nitrogen is a mobile nutrient. that just means that the plant can move its supply of N around within itself. so, when you clone, your clones essentially cannabalize themselves, since they have no roots to gain nutrients from. they use what stores of N they have and move it where they need it.
here's a wild guess: your clones start yellowing at the bottom, right? then slowly it creeps upwards? thats textbook N deficiency during cloning.
as long as your clones root, i'd not worry. one more guess though (about the 1st run of clones you did). i bet that when you took your cuttings, they were a little hungry for nitrogen. this (nitrogen starving) is a common practice and helps roots show up.
i've been cloning with a bubble-cloner for a while now, and the yellowing of the leaves always happens. as long as they stay erect (teehee) and i keep the humidity dome over them after mistings, they will root.

best of luck
-GG84
GoldenGraham84 Reviewed by GoldenGraham84 on . cloner and yellowing leafs Can anyone tell me why my cuts start yellowing within a few days of putting them in the bubbler. My first run rooted in seven days 100% even though they yellowed a bit. I started from scratch this time and bleached the bubblers, keep everything super clean. They dont look bad but the yellow leafs keep showing up. What can I do different? T Rating: 5