Could have sworn I replied to this.... oh how I love my internet some days!
Vet said the same things - nutritional, laminitis, seperation of hoof wall, fungal, result of a wound etc. But his hoof wall is in tact otherwise, isn't very thick but not bad for a TB at 3/8th of an inch. He's a coming 5 year old, so definitely not age and has no history of ulcers or anything that would affect him in that sense. Drinking just fine, drank normally while I had him in the barn and hair quality is dull but expected/normal for this time of year. He's haired up very well for winter, nothing abnormal. No chance of bad feed - he's on top quality round bales during the evening and I check the bales everyday as they peel new layers to ensure there's nothing in there. Have had horses on this field all winter, and for last 5 years without issue. None of the other horses seem to have a problem.
This is what makes this all so strange.... I'm going to take pictures tomorrow morning of it.
*Riding is not a sport, it is a passion. If you do not share the passion, you do not know the sport, and therefore are wasting your time*