It looks like slow rot. Your watering or conditions after watering might be wrong. I believe soaking plants for prolonged time is emergency action for very dehydrated plants. Doing that normally can lead to drowning your plants. If possible, regular misting or dunking for few seconds 2-3 times per week is enough during winter. Try to not water the spot where it was cut (plant base). Also find them bright warm place with dry air.

Thanks, Raxidor. I thought perhaps the bergeri wasn't getting enough water and therefore, had the shrivelled appearance. I soak my airplants in tap water with the tiniest pinch of fertilizer once a week. Soaking time is usually 4 hours. When it gets cold and gloomy, I just dunk them in water till completely green and remove immediately after that. I dry them upside down on a paper towel. The spot where they dry is next to a glass door, it is warm but in winter not too bright.

There is no way to reverse slow rot, is there? Many thanks! Meddy

Sadly tillandsias have no regeneration ability, everything infected dies.

I have several plants like the one in your top picture. For some reason, either one of them fell apart or a leaf fell off (I simply can't recall), but before composting the ~2" long leaf, I noticed that it had an almost microscopic bit of growth at the base. So I put this leaf where it got air circulation, where it could talk to my other plants, and where it got sprayed along with the other plants and very occasionally (since it was so small) bathed as well. That wee bit of growth took off and now a year or so later the plant is about 1" long and has its own pup coming out (the main leaf died off, but was no longer needed anyhow, having provided enough nourishment). So if there is any sign of life after you remove rot, don't toss the plant, give it a chance to start anew. At worst, it will liven up your compost pile.