Water would be my go to guess, but hard to tell from the video. The paint and brick themselves don’t really so any obvious water damage. Re-point it or have a mason do it. Do you have gutters? This is an odd spot for water damage like this. Is the crawl space damp because of this, or is there water getting in there from somewhere else? The damp from the crawl space could be the culprit, if it’s been this way for 100 years, water will find a way.