Q.How to deal with what appears to be root rot on lavender?
I bought about 1 month ago what appeared to be very healthy lavender plants (the butterfly flower type). I set these in pots – but ever since the flowers have become daily more brown…and don’t seem to be growing….I think in the beginning the soil may have been too wet…but ever since I have been careful not to over water. Should I prune now these ‘dead’ brown flowers and see if this results in new growth.
Will appreciate your advice…many thanks in advance.

Certified GKH Gardening Expert
You will need to treat the soil and plant with a fungicide. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
Overwatering will quickly lead to an infection that will need some attention. Repotting in fresh soil can help, but make sure to moisten the soil before hand and use a very small amount of water to set the roots in after planting. Don't water again until they dry out thoroughly. These prefer a dry, arid, and hot climate so try and get close to these requirements for the best results.
This article will give you more information on the care of lavender: https://www.gardeningknowhow.com/edible/herbs/lavender/lavender-in-the-garden-information-and-growing-lavender-tips.htm