I know it looks deeper in the photo, but the crevice is maybe half an inch at the most, and there was no "white chalky"
My concern is that regardless how deep, the 'crevice' was cleaned out adequately to remove all diseased tissue. And it isn't necessarily 'white & chalky'. It may well be if it's a fungal infection, but not if bacterial or otherwise(think I got that the right way round...). As it seems to be still messy looking & while can't judge trim from just that pic, it does appear the quarter should have been taken back a little more(as with the stretched toe.
I am a bit confused because my farrier has diagnosed WLD before... but this time he said my gelding's hoof was just too wet and it wasn't anything to worry about
Not there, so don't take my word for it based on one pic, but looks like it to me. True, wet environments can make a horse *more susceptible* to wall infection, but it's still wall infection. This looks like it's set in quite some time ago - seems to be in close to live tissue on a bit flared looking quarter.
When I was boarding in Nashville it was a strict 8 week schedule with more hoof care in between.
Like I said, depends on situation, but yes, 8 weeks could be adequate for maintenance, esp if they're getting 'brush up' trims in between. But I would be wanting a good farrier to see to these feet more frequently ATM.
I've read too much sugar in the diet will increase the likely hood of WLD ... do you think his diet has something to do with it as well?
He is on 4 quarts of pellet feed, 1 quart of alfalfa cubes, 1oz. of vitamin supplement and has a roll bale of grass hay.
Absolutely diet/nutrition is important. Yes, too much sugar &/or calories generally is one common prob - as with type 2 diabetic people, it's not so much that we can't hack a bit of excess or rubbish food, but when it becomes chronic, regular, & there are no regular 'hard seasons' to use up the fat stores that it can become a serious metabolic problem.
Can't comment on the pellets without info, but guessing they're grain based & probably high starch. Especially if that's the case, I'd be inclined to get rid of that, or if you decide to keep feeding, make sure that 4 quarts is over a couple or more meals daily at least. If the vit mix is appropriate & making a balanced diet for your particular horse, great. But it is very high in calcium(especially when considering alfalfa is too) & low in magnesium - poss needs more - and it has added potassium(also already high in alfalfa & many other feeds).