Thanks norwoodn. You motivated me to read up on the 5-1-1 and gritty mix here on gardenweb (there's a lot to read). Ended up repotting with a 5-1-1 based on "micro" bark (the "fines" were pretty chunky at the local garden store). When I went to repot, the old soil was so dense and soggy, a lot of the lower roots just tore off. So I guess that counts as repotting/root pruning. Now I have it recovering in the shade, we'll see if it can rebound.

First thing that I'd look to are iron deficiency and pH. Here's a chart with the basics of systematic leaf conditions. It's not always so cut and dry, but these are the basics... http://www.aces.uiuc.edu/vista/html_pubs/hydro/symptoms.html Since it's the easiest fix, I'd get a water soluble micronutrient product and use that first. A common formula is Iron, Zinc, and Manganese (not to be confused with Magnesium.) If it works, and you're growing in the ground, then check with your local county ext. to see if it's a common deficiency. If it is, then you know the fix. If it isn't then you'll want to discover what could be interfering with nutrient uptake. Common causes are imbalances where a surplus of one nutrient/mineral affects another, and pH issues. Good luck. :-) Oh, it could be herb. drift, but iron deficits aren't uncommon. Edit: Dave posted while I was typing... I basically agree. Especially since micro-nutrient supplementation is so simple, and plants usually respond quite quickly to their application, I'd try that first. If it's herbicide drift, they're damaged beyond repair, and there's no sense worrying about that until you've ruled out the easy fixes.

Not sure about changes in water quality, we are on town water and I have always used it for watering my Peace Lily. No recent house moves either and I just checked - we have both fluoride and chlorine added to the water supply. I switched potting mixes due to the aforementioned problem of yellowing leaves. Basically as a trial in a more open mix to determine whether or not I WAS over watering. I don't think I was, as all the roots were white and healthy (although rootbound). I'm debating whether or not to unpot the plant just to check the roots. But maybe I'll wait on that. I need to do a bit of research to determine whether or not I have her planted too low in the medium and if I have, I'm planning on replanting her in the correct position. I'll finish the watering experiment first though, just to rule that out.

Sorry for quick double-post.... To answer Hu's question about spraying: you are in a tricky spot because of the weather. As Silica said, you don't want to spray your leaves when it is hot (>75-80 degrees) because that can cook your leaves. My Meyer has been growing like crazy for the last 1-2 months but in Phoenix it is still 100 degrees. So, much of my new growth is deformed. I try and spray with water to knock the thrips loose periodically, but can't seem to keep up with it. In other words, you have few options during summer/fall flushes when you live in warmer climates like we do. I'm not aware of anything else you can do besides a rigorous spraying with water, multiple times a week as long as you are getting new growth.