Sounds like the inevitable run of bad luck.
I had three horses for 15 years and only had one incident that needed stitches. 1 problem in 15 years! I rode two of them EVERY DAY, hard, and one of them I trained for endurance on. All three were kept barefoot, were wormed, never had shots, were isolated at my parents small farm, and we even had barbed wire fencing! Fed them roundbales, drank well water, pasture, and fed general all stock feed during the winter.
Then we moved and my list and # of horses started growing! I lost those three within a few years, tornado, kidney failure, and old age. Cleared out the herd and now only have three again, in the last 10 months I've spent 10 times the amount of money on vet bills as I did the three I had till the day they died.
I think it just goes in cycles, brace yourself and SAVE SAVE SAVE for rainy days!
Hope they all get patched up and feeling better soon!