Thank you all for your input. Their feed and hay have stayed the same, so I don’t think it is dietary. Our farrier does a great job making their feet look nice, it’s just that they crack and split again in about a week. We have been getting a lot of rain lately. We have five horses here, and all of them are getting a little worn, but two of them in particular are the worst. I’ll look into the Hoof Hardener, where is it usually sold? Tractor Supply or most tack shops?