Induced low pasterns?

[Rivendell]

I was moving my rams around and drenching today, when I noticed that two of my previously fine rams were literally standing on their full foot (hoof + pasterns/heel). Both of them were affected in the back left foot. One ram is 2011 drop and the other is 2012 drop. Their feet were fine when I checked them last monday.
Before this year I had never seen or heardof this, but two other breeders in my area (close friends) have also reported a case each, exactly the same, in a 2012 ewe lamb and a 2012 ram lamb, same breed as mine (hampshire). They were both affected in the back right foot/hoof.
None of the four sheep are related in any way, but all are in the same region. All of them are up to date on ALL vaccinations and parring.

Could this be a vitamin/mineral deficiency, or something more sinister? I really would like to find a fix ASAP, because all four are show animals, and my best ram is in with the two with bad feet, so I'm a bit worried about them all!
This is in VIC, Australia, for reference.

 

[purplequeenvt]

What is the temperature right now? High temperatures and stress can cause a drop in the pasterns. I've seen big sheep come off the trailer at a show really down and then a few days later be completely normal.

 

[Rivendell]

Normal range temperatures. I'll check my boys tomorrow, however the other two have had it since february :/

 

[Four Winds Ranch]

Is it not possible that it is a hereditary trait for weaker pasterns? And maybe some have the a stronger gene for it then other and therefor get it sooner! Maybe it is something that runs in Hampshire bloodlines?
I had it happen to 2 of my ewes a couple of years ago, both were 2 yr. old, Tunis. I asked around about it and was told by a few people "Just a bad gene that sometimes runs in the breed, get rid of them and their offspring". I have since sold them and have had no problems with it again.
Just an idea!!!

 

[purplequeenvt]

A lot of the more popular meat breeds have a tendency to be weak the pasterns. I know that a lot of Tunis breeders struggle with weak pasterns, not sure about the Hamps.