2 clones from same plant same day same reservoir

What the heck is happening with the midget clone
Good root system as per photo

Can anyone help ideas please

Trunk rot most likely rock wool can get too moist and plat decays just above roots the fattening stem/trunk is the give away it rots the trunk which tries to heal getting wider right above infection
Ugly cousin of root rot and since it hit early toss it and start another better early than later when your plant was larger


Thanks heaps noted and I’ll give her the flick once again much appreciated