I just had my pool resurfaced in 2015 and in the last year it's developed a couple of stains that I'd like to see if I can get any pointers on how to remove. One type of stain is from pucks that were placed directly in the pool until they dissolved. The other seems to be... dirt? They're darkened areas primarily in the deep end where palm nuts drop, debris tends to collect, and the pool cleaner spends most of its time. However, these areas are completely unaffected by vigorous brushing, the cleaner, etc. so I'm not certain they're dirt. Nothing looks too bad, but the pool's surface is only a year old, and I don't like to think what it would be like if this pace keeps up for another 10 years. Any suggestions?