Skeleton and ghast spawn rate is constant in Nether Soul Sand Valleys

Everytime I've loaded into the Nether I've been bombarded with skeletons and ghasts next to my portal. I've tried digging away to get out of the Soul Sand Valleys biome but still see skeletons around every corner. The spawn rate feels about every second, and even if I've placed torches and made tight spaces, I find skeletons chasing me. I can't walk a few meters without running into these rapid spawning mobs. As soon as I defeat all the mobs in the area, twice as many spawn constantly.