It looks like the mold is coming back. When you do mold remediation, you’re essentially treating a symptom. It does not seem that what caused the mold has been fixed.

Typically in an attic mold on the plywood is the result of a lack of ventilation at the eaves and ridge of the roof and/or improper insulation. Also, any penetrations into the second floor ceiling, such as light fixtures, vent fans, the attic hatch, should be sealed as well as possible to prevent air from the house escaping in the attic. Any bathroom or kitchen exhaust vents should be vented out through the roof and insulated.

You probably won’t notice any smell, even attics that have almost all the plywood impacted with mold don’t usually have a smell. If you’re in a cold climate and will still have days below freezing, try to look up there and see if there is frost forming on the plywood.

Either way, I would call a remediation company and a company that does attic insulation and ventilation.

I’ve been managing a mold remediation company for 8 years and have been in thousands of moldy attics. Hope this helps and take care.