Aloe - help needed with problem

[Fuerte Rav]

I've got a NOID Aloe that I call the Spider. I was given a cutting about 10 years ago and have grown it, propagated it from cutting and seed and have several large clumps in my garden. A couple of months ago I overturned my wheelbarrow accidently and knocked a chunk off. No worries, I stripped off the lower couple of leaves and stuck it in another bed. Gave it some water and forgot about it. This is standard treatment for aloes here.
I have about 6 different varieties and all get treated the same and they all grow and bloom like mad.
Today though I noticed this new plant was looking decidedly unhappy and it's all happened in the last couple of days. I went and checked the other clumps of the same variety and they are all suffering as well! The other varieties are all OK.
It seems to start with random discolouration on one or more leaves. Then that area goes really soft, then it dries out. This is happening on old leaves and new. Affected plants are in different parts of the garden, different soils, different levels of sun and wind.
Any ideas as to what is happening? This is not something I've seen before.

This is the 'new' plant:


This is the 'parent':