Honestly, I think she is genetically predisposed... She has always been quite tender-footed, and in her dam's last years, she spent a good bit of time in boots because the mud would soften her feet to the point that they would bleed.
The vet was going to X-ray her the next time I had something going it, to see how thin her soles were. She is only 5. Barely broke, but I rode her on Sunday, only at a walk, and since then she was spending a lot of time laying down, but she has always layed down a lot, so I really did not think much of it. She RAN up yesterday afternoon, then looked a bit ouchy, but then seemed fine led in last night. This morning, I knew it was over.
Honestly, she probably could be managed, but right now, I cannot afford, either financially or emotionally, to work through this. In years past, I have spent THOUSANDS managing foundered horses, and lost them anyway. So, I am not in that position anymore, and I am putting her out of her misery.