Spelunker's Charms II adds a cave biome called the Mantle Caves where most of the deepslate is replaced with blackstone.

This seems to result in Oreganised ores not spawning in this biome which can cover large areas of the world, causing ores to be rare in these regions.

Perhaps a blackstone variant of the ores could be added if Spelunker's Charm is detected? Other modded ores do seem to just spawn deepslate variants in the blackstone too though.

A normal deepslate layer, showing that the ores are generating properly in normal regions.

A mantle cave layer, where the ores are not spawning.

EDIT: For the time being, I've made a datapack that lets the deepslate ore spawn in blackstone. I think the lead is close enough, but I am not sure about the silver. I'm probably going to boost the silver spawn rate in my pack anyways.