Too cold? soil too wet? level of soluble salts in the soil too high? reaction to something topically applied?

Over-wintering it where? indoors - outdoors - basement - @ what temp - how much light? Give us a little something to work with ....

Al

Temps: 65-70 F
State: Indiana (46181)
Location: Indoors
Light: West facing window (very cloudy this time of year)

I dug them up after frost shot them down, cut them back to a few inches, cleaned off the roots (they looked very healthy), repotted them in fresh potting mix. They have been growing very well.

I only water them when they start to get a little dry, but I did take them out and give them a good soaking with the garden hose.

The west facing window is a patio door. It could be leaking cold air at night.

Indiana.Matt
Matthew

A picture of the whole plant would be helpful.

This seems to happen to a lot of plants in the mint family when you try to move them indoors - it's certainly the case with basils. The plant also appears etiolated from a lack of light.

The cause is probably some combination of 1) low humidity indoors, especially when central heating is on 2) root dysfunction/rot from soil conditions being too wet.

Go back to only watering when it feels dry. Try making a clear plastic tent of some kind to increase humidity. A simple compact fluorescent positioned over the plant, as close to it as possible, may help too.