I took a look at the photo you posted earlier and think the crack you are concerned with is running from the middle of the frog up into the back of the hoof between the heel bulbs. If so this is being caused by deep seated thrush. I would not ever use Bleach, not even diluted, or Hydrogen Peroxide. Both will damage live tissue.
Actually I would try to not soak these hooves at all with how wet the frog appears now. There is a product called No Thrush that is dry and draws disease out of the hoof. If this doesn't work on it's own I can recommend other items. But that is what I'd use to start.
Then I'd pick up either the Quick Fix Hoof Wrap, the Deluxe Equine Slipper or a pair of hoof boots to try to keep your horse out of the wet. This will also provide a way to put a #2 Diaper into the wrap, slipper or boot and puff the No Thrush into it so the hoof will have treatment throughout the day. Disease is very painful and can be quite invasive if not taken care of.
The other issue would be the trim. I would pick up a Blackmaster Rasp and 2 F Dick Ascot Knives (1 left/1 right) so you can begin cleaning up these hooves on your own. Most important right now is to open the central sulcus to expose this disease area to the air.
I don't think radiographs are necessary at this time. What I think you need to do is start doing a rehabilitative trim on this horse, combat the disease and provide support for the healing.
There is a product I always use with thrush instances and that is from For Love of the Horse. It's called Hoof Ailments and is wonderful for assisting the body to heal the area.
I hope this helps a little. I do not work for any of the companies I've mentioned but do have a lot of experience in using them. I know they work or I wouldn't recommend it.