Lots of good advice
Attic ventilation is also a good idea
replacing sheetrock with concrete board or the waterproof drywall is also a good idea although I prefer the concrete board, mold if the spores are present will spread.

In my experience, its often less expensive to get the room then replace the drywall. Adjoining rooms may be affected as well.

Last major rehab I did had a major mold problem mostly explained by the tree thru the roof for 2 years without any action being taken. (We had mold in over 40 feet of exterior wall as well as 60 SF of roof sheating) Upon consultaion with a remediation specialist, we gutted the entire house to bare studs which were treated with moldicide/Fungucide after pressure washing with a sodium hypochlorite based detergent (read as a mixture of tide and bleach) and drying (72 hours at 140 degrees) , the house sat for a month and after final inspection the remediation firm signed their warranty. It was a messy and time consuming process but end result is 3 years and narry a peep from the homeowners. Yes, they were aware of the work that was done and the reasons behind it.

Redid all drywall, a new roof with ridge vet as well as a power vent due to our high humidity and heat during summer months. Upgraded ventilation system in bathroom and the entire house as well new HVAC and new ducting. no soffit vents, no ridge vent and no gable vents. The Bathroom exhaust was vented directly outside as was the dryer vent previously, the BR ducted to attic and dryer altough vented outside was improperly vented with too small of piping for modern dryers.

For me it was learning experince and one that I am glad did not learn from my own home.

The one thing I found interesting was in addition to the inside of the house, they cleaned all sidewalks, driveway and the yard section where the dumpster sat during the demolition phase.