Right, got back to it...
Firstly OP, it's very likely been mentioned here before, but for Justin, look up lamenessprevention.org and study all you can there. Hoofrehab.com is also a great resource. I haven't bought 'that book' yet - do plan to, as another resource to loan to clients. Yes, whether or not you ever plan to do the job yourself, I believe it's SO important for owners to educate themselves. It's not just about being able to evaluate trimming jobs & choose good farriers(assuming they're available) but there is a lot about hoof health that is down to the owner, not a once-6-weekly visit from a farrier.
Re the pics, the hinds actually don't look terrible to me, front-to-back balance. They are both somewhat long & crushed forward heels, tho not sure how much is camera angle(yes, it is hard to get hoof pics 'just so'), as heel looks good on the left hind pic showing the crack. Bars also appear overgrown, not trimmed.
The right hind does appear too long toed, shallow angled, heels might be too low - but esp looking at the whole horse, I sus it is from something 'upstairs', maybe a hip or sacrum prob. So maybe a chiropractic vet would be helpful for that.
That left hind crack, I think the main thing - assuming bars & heels addressed correctly - is that I would be 'resecting' it & strongly bevelling at ground surface. I marked your pic, the blue line showing approx where I'd trim - keep the resect as narrow as possible, but take all infected tissue if poss. There does appear to be seedy all the way around, at the ground surface at least. This will need topical as well as farrier treatment.
I've marked one of the front-on back hoof pics, to emphasise how distorted the quarter walls have got. As said, hoof rings can be caused from a range of things, not necessarily at all alarming. I think that the rings being on all feet(tho looks like farrier has rasped surface & they're not so obvious on fores) indicates that they are systemic - diet change etc - but that they're so much worse on hinds, actually ridgy, esp at quarters, is due to mechanics/imbalance.
Fore feet balance seems pretty... ornary. Heels are high & crushed forward, especially it seems, the right fore, and toes are also quite 'stretched', esp it seems the right. **Look up 'high-low syndrome' as it's not necessarily right for both to be matching, force symmetry on feet tho. Bars also overgrown. I marked red lines for the probs, green for where I imagine the toe walls should be if they were well attached. Oh and the left fore medial shot, I marked the hairline on that one to emphasise the dip at the front - this indicates P3 angle is likely too steep, pointing down at the toe, &/or that pressure at the quarters is 'jamming' the hairline upwards.
Shoes are flat bottomed & toes are set to the toe wall where it is now, so it seems some way forward of 'breakover', although(an illustration that you can't rely on pics alone) the sole shots make it seem there is little 'stretching' forward. As heels are obviously run forward but the heels of the shoes go way back to the widest part of the frog, there must be quite a bit of 'overhang' for the horse to be able to step on. The shoes also aren't quite straight, particularly the right one, the lateral bar is bent quite a bit further in & over the frog.
So... I hope these observations help you some, to learn what you're looking at & insight into what may be needed.