Especially, bleached white, industrially processed sugar & almost worst, corn syrup functioning as a sugar replacement but metabolically processed the same. 

I would strongly recommend to your tenants that they do maintenance on such things as bleaching bathroom tiles/grout to keep mildew down, and pulling out appliances to clean behind.

So bad that you spray 50 GALLONS of bleach over the entire interior to try to sanitize it BEFORE you gut it down to studs . 

If the levels legally require remediation you will pay for the testing and if they do not the bill will go to the tenant.You can also take the alternate approach of going into the attic with bleach or a solution of distilled vinegar and scrubbing the area that the tenant reported had mold.

Do i bleach, replace, or hire a pro?

Normal wear and tear is sun bleaching etc.   

After removing the carpet and engineered wood we saw stains all over the subfloor that had to be treated with enzymes, then vinegar, then bleach.

No garbage disposal, limit chlorine bleach, don't pour grease down sink.

If it is a white enamel sink, you fill it to the very brim with hot water and pour a good dose of clorox bleach and then just leave it to soak for awhile.

FYI for all making assumptive replies, this could just as easily be a situation where say the walls are erupting with mold and landlord is saying it's just a free houseplant and if don't like it was the walls with bleach daily, and calling any request for it being addressed as "blown out of proportion".