Hi Missouri..Sorry about your peps..
Have you done anything different than you were when the they were perky?
How bright is your north window? Is it obstructed or unobsturcted? Since north has the least light, and if there's buildings/trees blocking the sun, it means they're getting little light..Though Peps can survive in lower light conditions, IMO they do best in medium light..for instance an east window or higher.
What type of soil are they planted in? What size and which material are pots?
Peps are succulent plants, (they retain water) therefore a well-draining soil is needed..My peps live in a west window, well=draining soil in clay pots. A few are in plastic though. One thing about Peps, though they require soil to dry between waterings, they dote on humidity. If possible, take to sink and hose foliage (try not getting water in soil)
Do your pots have drainage holes? It's important they do.
Either your soil is being kept too wet or too dry. Before watering, check soil by sticking finger deep inside. If it comes out moist, then wait a few days, recheck..If it comes out dry, water..Check every 7 days to begin with..
2 wks is a long time between waterings..Unless you're using the wrong soil, or pot size is too large, or both, that could be the problem leaes are wilting.
Peps do NOT like to be overpotted..they seem comfy cozy when living in a small pot. Keep us posted, Toni

I don't know what type of soil they are in. They're in the same soil they came in when I bought them. They are in 4" plastic pots with drainage holes. I haven't changed anything since I bougth them. I usually water them when I stick my finger in the soil and it comes out dry. Sometimes that would be ~2 weeks. I will try hosing the foliage in the sink. I hope they pep up soon. Thanks!

Mine did wonderfully in my cubicle at my old job, then nearly died when I brought it home. Now it won't do well anywhere except under a grow light. Maybe they suddenly decided they want more light?

I've never had much luck with peps. My two favorites are the watermelon and the emerald ripple. It seems they do fine, then start to decline in a few months or maybe a year. The last one I had was an upright one that had small leaves (about 1" at the most) that were variegated. It was so cute. I gave it as much humidity as I could, and let it dry out between waterings. When it started drooping, I decided to water a bit more often. I misted daily. Nothing helped, and it eventually died. I've heard other people say they also didn't have luck with peps. They seem to be very fussy. But they sure are unique plants.

One of my peps seems to be perking up. It even has some very small new growth coming about.
My other one has lost over half it's leaves. They were wilty and mushy at the base. I was looking over the plant and it was very loose in the soil and could have easily just been pulled out of the soil. But, I noticed that it too had some small new growth on it. I put them both in the window to get a little more light to see if that helps. I hope they make it!

Would it be ok to trim off the wilting stems? One plant is coming back nicely but the other has 3 stems that have been drooping for weeks. They are very flimsy look as if they are on their way out. I just thought it might help the rest of the plant if I got rid of the dying stems?

I have been having the same problem with my Silverleaf peperomia, which has the exact same growth habit of emerald ripple, but it is in an east facing window, i have made attemps at both stem and leaf cutting in order to propagate in case the parent plant doesnt make it. whcih type of cutting has the best success rate?

Seacheo..I love Watermelon Peps, too..Its coloring really resembles melons..lol There are some beautiful Emerald Ripple varieties..Just got one w/pink in the center.

Missouri, yes, remove the rotted stems, ASAP. How do the roots feel/look? Are they mushy? If so, the plant is probably a goner..Sorry. Pep soil needs to dry out..this is very important..at the same time, Peps love humidity. But remember, Peps hold water so even though soil may feel dry, they hold enough water to provide necessary moisture..

Jmc, it's a good idea you took cuttings..Did you take leaf or stem cuttings? I've never rooted stems..
Filled up a tray w/well-draining soil. You don't want to use the oldest or youngest leaves for rooting purposes, try for the middle section..Dip in rooting hormone if you use it. Make a small hole in soil, then insert leaf stem in at an angle. Cover hole. BTW, it's best wetting soil before inserting leaves..sorry about that. Cover w/plastic, but make a slit for ventilation. Place cuttings in medium light, no direct sun..Keep on the warm side. When the soil starts dries, you can either add water, (carefully) or mist enough water to wet around stems. Good luck, Toni

I suspect overwatering too. I almost lost mine for that reason. It also drooped and wilted and lost a lot of leaves. When I bought a moisture meter and started using it, I foud out why - way too much water, although to me it looked like it was pretty much dry.
Mine is near a north-east facing window and is doing great but I live in a zone 10. In a zone 6, I suspect there isn't that much light coming in through the window, so it will need even less water.

Either less water, or a bit more light. My Peps live in a west window, so they mainly get afternoon sun..in summer, direct.
Though, I've seen Peps growing in a nearby conservatory, planted in a shady spot on the ground, their secret is humidity. Yes, the leave were huge, and spikes bursting everywhere..Toni