Could be a fungus like Vladimir said, could also be an insect egg or just dirt on a bit of fluff. However, I'm more concerned with how dusty the leaves are. I may just be dust or it could be the beginnings of a spider mite infestation. It's a good idea to wash off the leaves from time to time, like maybe every 4-6 weeks. Take them outside and hose them off, or if that's not possible, put them in the shower and shower them off with cool water. Then let them drain well and put them back where they were. It helps prevent spider mites as they're attracted to dusty plants. And your plants love the rinsing off!

DD has had lots of mold problems too from a roof leak and a basement flood. From our research and experience we learned that insurance companies not only do not cover the damage, but report the damage in a universal (industry wide) database making it impossible to ever sell so we were reluctant to report it. I'd seriously love to have someone refute this. She paid a mold remediation company $350. to evaluate the situation and we were looking at discarding a huge TV, genuine leather sectional/sleeper (the worst of it was in a basement TV room her SO had built for himself and buddies at the time) and over $5,000 for remediation. And that's after a brand new Pergo floor and lots of drywall had been removed. She knew someone who could place their industrial ozone machines in there and monitor them and the mold. Took maybe a week or two, but it actually did get down inside the furniture, etc. and kill it. She turned them up when she left for work and off/down when she got home. If you could leave and leave them running for a week it would probably work even better. Then we washed what we could with soap and water with bleach. I know there is a controversy about whether ozone is safe but just saying, it was an option that worked for her. Good luck. Sandy

There are enzymes that claim to neutralize pet odors from urine. Perhaps one of these was used. Realtors often use ozone generators to eliminate pet and cigarette odors before listing. Absence of odor can be explained. I suspect that if you were to use a wood floor scraper to remove some finish and wood off one of the spots in the foyer, you would get an odor. Nothing you've suggested as possible causes would make those concentrated spots on the floor, especially when the surrounding areas look to be completely unaffected. As I wrote before "Maybe there was a leaky pipe at some point but it didn't cause these stains that are textbook examples of pet stains.". Maybe there's a leaky roof. Maybe there's been leaky windows. These should all be investigated, but with 36 years doing only wood flooring, and being called in to look at all manner of issues, I'd say it's pretty clear to me that these are from pet stains. I disagree with GreenDesigns somewhat. I don't know the pricing of houses in the area but being an hour or so from DC must affect prices. It looks like a cool house and property. Paint color is a poor reason to reject a house since it's easy to change (and most people want to make it their own). The roof looks sketchy but not too hard to replace. The foyer floor would have to be completely replaced, painted or maybe stained really dark. The other floor areas could be evaluated to determine whether furnishing or rugs would hide some of the stains, patch if necessary and refinish. Good luck!

The Yelp comment I read seemed to describe in an uncomplimentary way your demeanor in speaking with two potential customers, the author and his neighbor. Well like this forum board as well as other areas of life you have to be able to read between the lines? He said I was "condescending to his wife" --- he wasn't there on that visit, so he's taking things I said to her out of context. He was recommending things to his neighbor that she couldn't afford let alone to be able to fix her system which in my opinion was a botched install from another contractor (maybe the builder?) , like he had at his house (not installed by me but another contractor) -- how the differences of opinion became about. He didn't like what his "previous" contractor was telling him which is the only reason I was over there. What was he recommending? most of what this was about was a humidifier that wasn't working at his house. The needs of a humidifier for my location? Maybe two weeks to a month of use per year. So the whole gist of condescending was related around a humidifier, yes. Because I told his wife that this climate is so humid that a "humidifier" is a waste of money for this climate. The guy in my mind didn't like looking like a ______ in his wife's head so his rebuttal after I left was to give me a bad review on yelp, that litteral means " a difference of opinion ". The neighbor? she didn't have the money to do what I recommended to fix her system let alone what her neighbor wanted her to do. Her system had a plenum coil. What is a plenum coil? do you know? The problem was condensate leak. If not fixed properly, my company become liable for these kinds of things. They always blame the last guy that touched it. So due to the install hackery, I wouldn't do anything more than recommend the Evap coil replacement which included proper condensate drainage of which she couldn't afford. I service the Katy, Texas area. (sometimes my fat fingers get in the way... an honest mistake.) no flags for mispelled words on Houzz. Certain people call me and want to "tell" me what to do. So when I oppose them, because I view it as a waste? What is often a rebuttal to things like that -- they never call it like it is. Same thing goes for UV lights, air scrubbers, smart thermostats via wifi or litterally tons and tons of garbage you don't need or telling me to do something that isn't going to "fix" the actual problem. Like: moving a thermostat, installing sensors --- let's ignore the real problem and install a gimmick based gadget that won't work for this climate except maybe 2 weeks to a month of the year. Reading "beteen" the lines? what is it worth? The gadget market is a billion dollar industry. It's not what you know, it's what you know for sure that just isn't so...