Thanks folks!
Taken him off the conditioning cubes - just basic rations - happy hoof and a tiny slop of speedy beet as before and he isn't as 'hot' already - was a bit reticent when the vet. suggested - NEVER again! The lumps are not as obvious but still all over him. They are like solid nodules...
My 20 year old arab boy (not ridden) has had hard nodule type lumps come up all over him - only thing I've done differently is start him on cond. cubes (vets advice) a week ago - hes dropped his topline and looks 'older' - is this a protein overload? Have stopped them tonight - will speak to vet...