Red stains obviously sounds like iron deposits. What was their reading for iron levels in the water they tested? Realize that water standards are only about water safety (i.e. will someone get sick if they drink it). They have nothing to do with what is typically deemed satisfactory regarding taste, odor, hardness, etc. Specifically ask them what they are referring to regarding 'allowable levels'. Levels for safety of iron are much much higher that what is tolerable for aesthetics and taste. Anything above 0.5 ppm of iron is a whole lot of iron and will lead to staining, but you can drink water with many ppm's of iron in it and be 'safe'. Since you have PEX plumbing and likely no iron pipes, the iron source is likely from the water source itself or from accumulation upstream of where your service joins. Do your neighbors experience this problem too? That will give you a clue as to the source.

soot indicates a design flaw. It could be that the fireplace opening is too large for the flue size, The firebox isn't designed properly, the chimney is too short/exterior chimney, or the house is so tight not enough air can exit through the chimney. Of these possibilities, by FAR the most common one is the height of the stack is too short. Typically most chimneys are constructed to minimum code, which is inadequate for proper operation. By minimum code, I'm talking the 10-2-3 rule where a stack must terminate at least 3' above the roof where it exits, and at least 2' higher than any portion of the structure or roof within 10'. This code is a fire safety code for sparks and so on and not really a good one for producing proper fireplace performance. If the stack is an exterior stack this problem will be compounded and smelly downdrafts are likely to occur when the fireplace is not in use. A properly constructed chimney is one which: a. terminates at least 2' above the highest portion of the home. b. at least 4' above the location where the chimney exits the structure. Take a look at very old homes - where fireplaces were actually used frequently. These homes don't have problems with draft, they don't have soot staining the mantle, and they don't get downdrafts (unless someone has modified the original fireplace and chimney design during a remodel etc. of course). They also don't have chimneys located outside of exterior walls and they don't have chimneys shorter than the structure - at least ones designed for fireplaces (some chimneys on old farm houses etc. may have been used for cooking stoves etc. and they're smaller and may not follow these guidelines). Look at higher end older homes, pre-1950. the chimneys are tall, sometimes very tall, they exit from the roof usually inside the house envelope and they are higher than any other point on the home. Unfortunately, today most "chimney professionals" or masons don't understand how to build a proper chimney and their most common canned and usually wrong response is "it needs a stainless liner!" If you purchase this home and attempt to correct the smoking problem, be aware that those who suggest a liner to solve the problem are likely incompetent and you need to keep looking for a competent mason/chimney professional. Good Luck!

I could guess here, but I really would need to see the problem before saying anything with conviction. Was the finish an oilbase (solvent-type) or a waterborne? Sometimes a waterborne finish will stretch at the board seams when the boards shrink and exhibit what we call WLS (white line syndrome). Or, it could be a contaminant interferring with the finish bond or stain that was not entirely dry. Hopefully your floor guy will be able to tell you the cause.

The product I swear by for stains in upholstery and carpets is called Folex. I have taken red wine, orange pop, pizza sauce and lipstick out of both carpet and sofa in the kids' rumpus room. I bought some for work and we removed vomit stain from the seat of one of the tour buses with no effort. I buy it at Canadian Tire and Home Hardware in Canada. I'm not sure who else might carry it.