Not rooting in bubble clonernot dying anymore

set up

submersible heater keeps water at 79F
20-30 gallon air pump going into two air stones
RO water
keep plants around 1/4'' above the level of the water.
8 clones
1 26W 6500k floro light 2 feet above clones on 18/6 cycle

I cut clones bout 3 weeks ago 6 of 8 of the originals have been replaced because they yellowed up to much or started to shriveled up, or got blackish brown on tips of small growth. they dont seem to be dying any more just not rooting.

At first i tried to adjust the ph to 5.5 to 6.2 and two drops of super thrive in 5 gallons of water but the ph was all over. I read that i can just use plain RO. They have been in plain RO water for a week. the ph of RO water after a week is around 8 originally it is around 7.2. Do I need to lower this?

I cut clones with a clean knife then cut a 45 deg angle on them under ro water then scarped up the stem a little in one spot and set them in some cloning gel for 30 seconds. and put them in the cloner

a few day ago i ready about splitting the stem ends so i did that trying to get them to root.

The newer cut clones were cut from budding plants so this will make it harder

here are some pics, any suggestions why they are not rooting

Id throw about a 1/2 teaspoons worth of rooting hormone powder into the water.. and take out the immersible heater, and make sure the room temp is about 75 degrees..other than that looks good, should work.

Best of luck

Will 1 or 2 drops of super thrive per gallon work? or should i use some of my cloning gel? or get something like cloneX. why do you not like the heater?

I am still not getting roots. they are yellowing up a little but now but not dead yet. i took the heater out room temps are around 75 to 80. i have some h and g roots excelerator on the way for my coco grow. should i change the water and put some of that in i hear it works great.

clones are taking a turn south. this stupid bubble cloner I made wont work. any ideas i need to figure out how to clone buying clones every grow is expensive.

I have never tried RO water but I had the hardest time getting my clones to take root, tried every 100% sure to work method out there. Nothing worked until I switched to spring water(only for the cloning). I have had great results everytime since. Couple gallons of spring water is about 1.50 , may not be the answer for you but it's worth a try.