I know that we don't have the best water because of lead and other chemicals. 

Your ac condenser and evaporator coil were not designed for different mixtures of crappy Chinese refrigerant and the two different chemicals will react. as all chemical compounds do when you mix them.

@James Lord My grandpa was on the chemical engineering team that patented these!

I tried multiple chemicals including Comet to remove it, but didn't worked.

Do you guys have your cleaning service take care of rhe cleaning and chemicals?

I have also asked her to send me information of what chemicals she used to bomb the unit as well as dates.

Cheaper options include using chemicals like Odoban or trying an ozone machine to clean the area.

Certainly, we can all agree that every segment of society has a few bad actors.However, in your post, you set out haranguing other landlords (that posted above, as you state) for some perceived wide-ranging ill that there does not appear to be any evidence for, at least on this thread.To baselessly condemn the entire profession without that merit, to me, does indeed reinforce a false narrative.If I were to muse publicly, as you did, that since a few individuals belonging to an industry (or ethnicity) did wrong, paint them all with a broad unilateral brush and declare “and people wonder why (that group) have a bad name”, I’ll bet you’d use a harsher term than “false narrative” to describe that sentiment.Landlords have a very unfair negative public image because of a very small percentage of individuals in the industry, and you are not helping.

You couldn't be bothered to use a 50-year-old weed control chemical on an overgrown yard because you believed some quack somewhere that told you it might cause cancer.Now you're hypothesizing that your dirty tenant brought a breeding population of rats with him.Come on, Peter.

I live in the CENTER of 6 major chemical plants including BASF, Dow ,BP... the rental market here is KILLING IT, because you have the average Joe making 75-125k a year!