My new stucco house was just painted by a painting contractor and now has unsightly stain streaks. Do you know what possibly could be causing this?

Stucco and mortar joints contain hydrated or lime, a dry compound added to improve the workability of these materials. If the high alkalinity of the mortar, cement mixes and concrete is not addressed prior to painting by your painting contractor, a reaction can occur when moisture is present, resulting in peeling and burning stains.