The difference in the two is the amount of moisture in the crawl space.

Also other signs of moisture like bubbling or cracking on paint.

The white on the redbrick is a sign of moisture though. if this is interior then I would recommend the drylock and perhaps a dehumidifier. though you could ignore this for 20 years and be fine.

At the start of tenancy did you and the tenant sign a disclosure on mold and moisture hazards?

Just a thought: keep an eye out for moisture in the drywall.

There definitely is moisture behind the walls.

Things to look for is a waterline on the walls an excessive amount of moisture damp floors walls bowing and cracking and the worst mould. 

Though it doesn't address repairing the foundation damage, it may give some insight into managing basement moisture in general:

"Moisture and dirt are entering the basement near the stairwell""Additional support columns/beams lack visible hardward securing them into place"Engineer noted there is no structural component dug below freezing level on any of these supports which would need to be done to get the foundation supports to code"Signs of water penetration noted on the basement walls"Picture showing proximity of nextdoor house"The soil slopes towards the foundation, or is flat, and must be corrected to prevent water from finding its way to the foundation" (This is the side of the house with the failing retention wall in the basement and has extremely limited access) The engineer recommended potentially just paving cement between the houses to seal it and recommended against a french drain as installing it would go below the level of the foundation already.  

I presume you have considered other common issues with basement units such as moisture, separate entrance, etc.