I use Happy Hoof and Formula 4 Feet for my cob and Section A who both have laminitis and the others all have Happy Hoof. Their quality of their hooves has dramatically improved.
you could try D L Methionine and gelatine, and apply cornucrescine up to twice a day. should see dramatic improvement in 4 to 6 weeks. farriers formulae, formulae 4 feet are all good. back to basics good food, well wormed etc you should see a change soon. it takes 12 to 18 months to grow out the old foot. And good regular attention from your farrier (every 6 to 8 weeeks)
I use Biotin mixed with zinc and methionine on my horse with collapsed heels and it really has helped him - to the point that every 5 weeks we can see the heel growing. Farrier is really impressed (but then he would be as he recommended this combination rather than F4F etc). I do also feed Top Spec Comp Balancer to ensure that he has proper diet anyway - the extra biotin is to support this.
I use a Biotin supplement (that has all the other necessary ingredients to combine and become effective) with absolutely brilliant results. The problem is that what works for one horse may not work for the next, and that applies to the most expensive product to the cheapest.