clone tops dying

Ive never had this problem before but i am working with new strains. It looks like instead of taking energy from the lower portion of the clones the tops of the clones are yellowing and when they root the tops are pretty much dead but the rest is just fine. Can anyone help me with this please.

Are you feeding them a light nutrient solution? Do you gradually take the dome off the tray?
Also be careful some rooting plugs(if you use them) have pests in them right out of the package.
Yes you Root Riot with your root aphids!

It's because the RH is too high causing the growing tip to rot. Remove domes you don't need them unless its winter and you need extra heat,no sprays etc.

It could also be from too much light at this time.