Question on water odor - Extreme newbie here

[BoSox9]

I'm a brand new hot tub owner (as in only had the spa for 2 weeks).  I have a Jacuzzi J-235 if that matters.

I filled up the hot tub for the first time, and added the recommended starter chemicals.  The next day I noticed a brown ring at the water line and the ring was oily, for lack of better word.  I wiped it off with a paper towel but it took some rubbing.  It tended to smear before wiping off.

Fast forward to this week and I've noticed a smell coming from the water.  I don't know if it's mold or if its something else.  I noticed the ring appearing very faintly again but being new to this I don't know if it's simply organic scum or related to whatever caused the original ring.  Full disclosure, the first week I didn't use enough chlorine (I eyeballed the measurement and was way off) so since then I've added about 4 tablespoons of chlorine to my 375 gallon hot tub (2tb Wednesday, 1tb last night and another just now).  The foul odor still persists.  I have a UV light and ozone sanitizer and I'm told that these burn chlorine so I don't have a way (that I know of) to know if I'm using the right amount of chlorine or not.

My other problem is I don't know what all mold smells like.  If I had to describe it I'd say somewhere between wet dog and oil.  But it could just be that the oily stain is weighing on my mind.  So I guess my questions are - is the brown ring on startup simply part of the startup the first time water is pumped through the equipment?  And secondly, any suggestions on what to look at that might cause a foul odor?  It's not overwhelming, but its enough that you can smell it when you're sitting in it.

Apologies in advance if I left out any info - please let me know if there is anything I can add.  Thanks!

[Ahhsomeguy]

Hello BoSox9:  What you should do is purge the plumbing and jets with a reliable and effective product.  The spa manufacturer you mention is very aware that this procedure should be performed on brand new delivered hot tubs to get rid of any colonization of bacteria, mold or other organic particulates that may be contributing to the brown slimy sticky stuff and the mold odor you seem to be experiencing.  People can’t imagine that a brand new hot tub can have contaminated plumbing from the manufacturing process and storage prior to delivery at their residence.  Study up on biofilm in hot tubs.  Based on what you are describing, this is yiur problem.  However, a good purge and it is gone.  For now, but it will return no matter how well you maintain your hot tub water.  Yiu need to perform this purge process every 6 months or so for best overall water maintenance and water health. Yes, you do need to dump the water after purging.