Divide the building with a wall, front half cabana bar, put a side door in to the back, 5' wide, from the door you'd have a vanity, then toilet then shower, last 3 feet a full length sauna. toilet, Outside on the back wall put a rack and cabinet for pool equipment and chemicals.

I then attended Purdue University and received a degree in Chemical Engineering.

That does look like it could be the sheet of underlayment that is high and the door has scraped away at it - check the bottom of the door - it will have matching wear marks.If that's not it, then perhaps it was a chemical conflict... certain vinyl and rubber can often be incompatible when moisture is introduced.  

You can go with the chemical treatment which is cheaper to get rid of them but you have a greater chance of recurrence.  

The lender that I decided on is Shawn Huss with Chemical Bank.

As I understand it, in heavy sun it also can break down and become toxic, with through-the-skin chemical transmission.

Can anyone share with me their experiences going through Shawn Huss at Chemical Bank?

A full-face, chemical respirator in mandatory!

Fill in all holes with fire retardant caulkInstall ABC dry chemical fire extinguisher in all kitchensInstall battery smoke and carbon monoxide alarms in every apartment of sleeping areas and furnace roomInstall 110V interconnected smoke alarms in hallways and basement.

Depending on who gets in the hot tub, can drastically change the water quality.  1 person that has been out hiking through the park, sun tan lotion on etc that jumps in a hot tub, can leave enough organic matter that will use up the chemicals as perhaps a couple that uses it every night for 5 days, but they jump in clean and aren't doing the wild thing.