Limestone Foundation Deterioration

I have a large building on a limestone foundation. The interior & exterior walls are covered with some sort of cement and painted with white paint, I am assuming this is a waterproofing paint. However on an interior wall near our gas meters the wall has crumbled and exposed the limestone blocks. What type of material do you recommed you use as a Plaster type mixture to fill in where this has broken off and to patch this area. I am planning on doing this and then repainting the walls with the white paint and then the floors with the gray.

Gday, you should make sure that there is no moisture in the wall causing the deterioration. If so your efforts will be futile. If no moisture then I would expect a cementitious filler would do the trick. May need pinning or being limestone you could carve out and replace a whole block.

thanks!