Any help or advice much appreciated.

About half the cuttings look like this the other half look fine.
rockwool blocks, clone start, humidome, 3-4 times daily misting.

are you keeping the rockwool wet?

yeah and RH doesnt go below 90%

i would only mist them once or twice a day, u want them to have insentive to drop roots.also in your 3rd pic i would pull off 2 more of those bottom leaves.how old are they?

Cubes are too wet . Have them at about 40-50% max at all times including when u first put the cutting in.

i put 15mls of water in the cubes when i put the cutting in and 10 ml every second day. they are pretty dry. sometimes i wonder if too dry.
the first 2 cuttings i took only took 4 days too root, the remaining 15 have jsut started callusing so few more days, the 2 ive potted that already rooted still look like the freak one in the humidome.

an started misting 1/2 hr before lights on with water and 1 hr before lights out with 1/4 nutes