My clones are yellowing and dying

IMHO they need more oxigen

They are looking fine, it is said to cut from the lower part of the mother plant and before you fertilize to encourage faster rooting. I would not say they are not doing the worst and look good to me. I would feed them once a week with 1/3-1/5 strength recommended. Once they get some roots they should be fine and transplanted asap. I would not be using a sealed humidity dome on them though as they need the fresh air and all that trapped RH can cause issues. I full agree with the statement below that over watering can be really hard on them, you will notice mutated weird new growth if this is prolonged for a while. The clones I did a while back where cuttings I placed in water for a few week then into soil and they all lived. I scraped the stalk and diped them in a .1% IBA rooting powder. I transplanted them out in the neighbourhood area and all of them where stolen lol.

How often do you feed them? and with what? Just water and Clonex? I never used spray, but I used to just mist them with water, Other then that, during the planting of the cuttings the plugs would have been soaked in nutrients for 24 hours, and after that I would not feed them for at least a few days, usually only twice before they are ready (10-12 days) I think I used similar (brown) plugs, but you will have to figure out by experience how much your plugs can hold. Put the bottom of the plug against your cheek, and if it's moist your good.. They need to work in order to grow roots, over doing it with water can really damage the cuttings. And misting once a day to keep the moist/humidity up. Watering by soaking the whole tray of plugs into another tray for like 20 seconds. I kept these in closed of boxes by the way, trying to keep the humidity high.