I'm currently a bit confused - I have three lavender plants (not sure what kind, but I think it may be Hidcote) on my balcony. Two are placed in one container and one in another. They were bought on the same day from the same place, and the containers are placed very close to each other, so the plants are exposed to the same weather. The soil is the same (peat-free compost-based soil mix, coconut coir, vermiculite and perlite with some bonemeal and composted chicken droppings) and they are watered at the same time and with pretty much the same amount. Both containers are crowded (I went for a cottage garden feel), with a rose in each, and some herbs, some perennials and some annuals. I understand that lavender, while being a great companion for roses, does not always appreciate the same soil as roses do, but what I cannot understand, is how the lavenders that live in the first container are pretty much dead while the other one seems to be doing fine (it's not exactly thriving, but it has grown and it's blooming).

We've had almost no sunshine and a lot of cold weather and rain this far, so I don't expect any of my plants to be particularly happy, but this is just depressing. I've had some issues with what I believe to be fungus gnats in a window box, I've seen some around the second lavender - the gnats appeared a couple of weeks ago - could they have damaged the roots enough to kill them? I've put up some sticky yellow stuff to catch the insects and added some nematodes to the soil, so hopefully that particular issue will be gone in a while.

Also, I'm planning on throwing the two dead-ish ones away tomorrow and replace them with new ones - is there something I can do, save replace the soil (not really an option) to prevent this from happening again?

Container 1:






Container 2: (to the right of the columbine)