I remember thinking, "wow why would anyone STAY in grad school to get a painful PHD in Chemistry when companies are so awesome to their employees?"

I have a bachelors degree in Chemistry and I love my job.

What I will address is chemistry.  

(I agree it's a good sign that some tenants have been there for a while, but they may have had a special relationship with the previous owner, they may "test" you and you may have different chemistry with them, etc. )I think you're absolutely right to start improving the property as a way to justify increasing rents to the tenants.Tenants aren't idiots, they mostly know if they have below market rent.

The previous tenants were trying to conduct a chemistry experiment with marijuana and something exploded causing the fire.

I have a degree in biology with a minor in chemistry, so my college experience doesn't translate well to the business/investing world, but I love to learn new things! 

I believe there is one Canna Kings and Good Chemistry are 2 places you could reach out to and ask who their landlord is.

(don't know my chemistry well enouh to know what contains carbon),  but you implied that shingles are inorganic and cannot have mold growing on them. 

I graduated last year from a top 15 American university with honors in Economics (B.A) and Chemistry (B.S.).

The successful bidder was initially delighted to find the Maserati in the garage, once owned by the former house owner who had a substance abuse (aka "living better thru chemistry") problem.