Hoof Wall Separation

One of our mares (in the 10 year old range) has recently developed what looks to be a separation within her hoof wall – it isn’t the white line, rather the internal and external portion of the hoof appear to have separated. It is happening on the outside quarters of both of her front feet. From above, each hoof looks well trimmed, sound and with no cracks/flares. From underneath, the feet look good too, except for this separation. The feet look symmetrically trimmed and seem fine aside from this issue. She is sound, not lame nor sensitive to it at this point. But I want to nip this problem before it becomes a real one.

I’m wondering if her hooves may have been damaged by some of the thaw/frost cycles that left really sharp and hard frozen mud in their sacrifice paddock? She is on the heavy side, but she certainly isn’t over-fed (she’s real thrifty?). Perhaps some nutritional issue?

So far, I’ve knifed down the inner section of the hoof wall to the level of the sole, and I’ve kept the external section of the hoof wall trimmed close to level with the sole as well. My thought was to take some of the pressure off of it so as to not encourage any further separation. I’ve been pretty conservative with this, since I’m not sure of what’s best. We also pick our horses’ feet daily, so we’re always keeping it clean and removing anything that might get in it (rocks, dirt, manure).

Has anyone seen this issue or heard about it? Any advice or resources that I might look to?

Thank you.