One corner of my house plaster wall is starting, this Winter, to show condensations. As you see in the first picture below it's like drops of water starting to form. This is the stair area going to the basement. The worst wet spot seems to be the corner starting the foundation block and under. I've been living in this house for a long and never had this before. No visible cracks or leaks in the outside brick wall - patches already. Not related to rain. 70 years old home in the Toronto area.
Two things changed recently -
- Last year I did insulation (injection - outside & inside wall) through Brand Insulation in Toronto.
- Also there was wall paper in this area before which I removed and repainted.
Not seeing issues that bad in any other parts of the house, this stairwell area is a little cooler compared to the other parts of the house.
Appreciate any advice on what may be causing this.

