House Plants/Peperomia obtusifolia
I have a peperomia obtusifolia that I've had for many years (two pictures attached). It's in an 8 in plastic pot in regular potting soil in a north window in my first floor bedroom with another larger peperomia next to it that looks great. We live in NE Ohio. My husband repotted it last spring & says he added either vermiculite or perlite to the soil. He's not sure which. I run a humidifier about 12 hrs per day & keep a table fan and ceiling fan circulating the air (but not blowing on it). I water it when needed (usually every cpl weeks or so) using distilled water. Have not fed it in a few mos since it is now winter. I use a Moisture Meter. It's been doing fine until just recently. When I went to water it the other day I noticed that one whole side of the plant looked basically dead. The stalks and leaves on one side of the plant are very limp and brown, basically dead looking. Some parts look worse than others. The other side of the plant looks totally healthy! I will say it is the side closer to the window that looks better although am not sure if that's the problem. I'm just concerned wanting to make sure it doesn't have some kind of fungus or something that I should be treating it for so it will get better plus & also so it won't get into the other one. Unfortunately before I got a chance to take these pics, my husband got to it first yesterday & cut off (with a sterilized knife & he treated it with cinnamon) a huge section of the very worst dead & wilted portions so you won't be able to see the worst of it in the pics. But I'm sending the 2 pics anyway. If you can enlarge them you can see where the sections were cut off. Those were really bad looking. Just brown & dead. This has happened fairly quickly. I'm perplexed. I'm not quite sure what to do.
I see your plant has some droopy stalks. I believe they are that way because they are top heavy. All the leaves are on the top and weight the stalks down.
I keep mine on my south facing enclosed back porch and it stays very healthy. I know the books say low light but my experience is they need some sun.
They sometimes wilt because they are not getting enough oxygen to the roots. Next time it is repotted you need to mix perlite in the soil at a ratio of 1 part perlite to one part soil. Perlite is the white pellets that look like Styrofoam but it is a volcanic product. It does not deteriorate in the soil, vermiculate deteriorates and does not get as much oxygen to the roots. Succulents need well drained soil with lots of oxygen. It is too early to repot it now and if you do in the spring don't put it in a larger pot just wash that pot and put it back in fresh soil with perlite.
In the meantime make sure you moisture meter reads dry all the way down to the bottom of the pot and then do not water it for 2-3 more days. Dry soil has more oxygen and will allow the plant to recuperate. Also do not allow any water to sit in the drain tray after watering it. It does not like soggy soil. Good luck!