Firstly, how frequently do the horses get trimmed? Assuming that they were well trimmed(which unfortunately I'm not), they're well overdue. They're quite badly balanced, long flared toes, long, underrun heels. Good, regualr trimming, to get & then keep them in shape would go a long way for starters. Allowing them to get/remain in that kind of form will add to the mechanical stress on the compromised hoof capsules... as well as elsewhere. *Not judging you or the whys & wherefores BTW, just telling what I see.
The rings & ridges on the hooves, the 'micro cracks'(making hooves appear dry & shelly), the stretched laminae & the flat soles in front half of feet all lead me to suspect that diet, nutrition & metabolic problems are at least a substantial contributor to the problem. Do some reading on 'sub clinical' or 'low grade' laminitis. Safergrass.org is one good source of info on healthy feeding, esp as it relates to hoof health. Hoofrehab.com also has a lot of great info, including a page on diet.
The worse 'crack' pictured, that looks like it's been resected, possibly needs further resecting & treatment of seedy toe. The 'x' scorring on the cracks are not effective at all IME.
The old farrier came out every six months; we switched to a new farrier awhile back (the old one was , and he's only done their feet twice so far - in March (a slight trim, as they'd just been 'done', and removing Magic's front shoes) and again on June 14th. I wish I had a picture that I could demonstrate with, but he really does trim them quite well - these two mares just don't have a lot to work with, and seem to grow especially fast on top of it.
I'm aware of their nutritional issues, and straightening that out is a work in progress - we have no way of graining them each a prescribed ration ('least not that we've figured out), so they get mostly pasture and mineral blocks. (And with Tanner laid up and kept separate, she actually gets hay, a mineral block, and grain + joint and hoof supplements).
I'd love to say that I could grab another farrier and get a second, in-person, opinion, but there's only three farriers that will come out to this area -- Our current one, the old one (who really was doing a kind of shoddy job), and a lady that is widely known to be a hack.