Those are abcesses and they are caused by your horse's feet being unbalanced.
For starters, he had too much heel and quarter. Once the heels and quarters are taken down to where they should be, it's going to become apparent that his frog and toes are stretched. He'll have some toe to take off the bottom, but he's going to have toe that needs to be brought back from the top...you won't be able to take it all the way back w/o making him lame...so you're looking at 2-3 trims to bring the foot back to where it should be.
Also, when you get those toes back to where they are suppose to be, they'll stop cracking.
Abcessing, particularly chronic abcessing, is always foot imbalance related.