Do you have a hygrometer to tell the humidity of the dome? Some strains are tough to clone, Should also have indirect light not sure if you have them in direct sun or not. Take the dome off a couple times for the first few days and mist them, exchange the air, and you may also want to trim or limit the size/number of leaves you left on the clones, They need roots to supply water, and they dont have any... So the least amount of leaves while still surviving is key. Leaves also transpire water when there are no roots (hence the dome and high humidity) so you want to keep that humidity high to provide water to the leaves through transpiration vs. roots) Like I was saying those, some strains are tough, some are super aggressive and root very quick, sometimes its a matter of overwatering your medium while trying to keep the dome wet and your stem starts rotting. I've used no hormone for years, I do now but didnt for a long time and havent had issues, Ive rooted in cups of water alone, and also had very good survival % in those bubble cloners (like 99%+) So try a few different ways, and be sure to double check you are cutting them in the correct spot. If you can, pictures would be really helpful of your setup so people can help you better. Good Luck.