My English Lavender is dying..

So I'm a new gardener that grows herbs used for distilled essential oils. I am growing my plants in growing zone 7a in South Carolina. I have a total of three English Lavender plants that haven't reached the flowering stage yet. I have them planted in a raised gardening bed, with two organic soil mixes designed for herb plants. The lavenders are planted in a straight line with about ten inches separating them. We have had about week of rain with some small amounts of sunlight in between rains. At first thought, I was thinking that maybe they were getting too much water, however, they started developing black stems and the leaves were becoming discolored before the rain came. Now there is an entire portion of the plant that is dead looking and this morning there was fuzzy grey stuff which could either be webbing or possibly fungus growing on it. I'm very new to herbal planting so any help on figuring out what this is, and how to address it would be much appreciated. I've enclosed a couple photos to give a visual of the plant including two close ups. Also, the confusing part is the other two plants on either side of the sick one is perfectly healthy and growing great.

I've had so much lavender do the same. Imo when they get like this it's over- just chop them, replant and move on. The rain and the lack of sunlight let a mold or fungus get them. That's why I keep my lavender in well drained pots now. Too cold, too wet, too dark I can just move them indoors for a while. It can be a fussy plant, but if you get it in a sweet spot you never have to mess with it again. It's just hard to find the sweet spot. I'd look into improving your drainage in that spot, and be warned- that black ick can spread to the healthy ones so I'd clean the dead ones out quick.

Anyone else please feel free to chime in though!

Tried growing lavender in pots several times but too fussy for me and since I'm not crazy about the fragrance anyway, just quit trying although I still plant some typical kitchen herbs every spring.
Based on a little research though, I found the following with the following three things emphasized over and over: "Hot, dry, and high". Also, you might want to try checking into species that may be more suited to your immediate growing zone or area. Although English Lavender is the type most often seen in our local nurseries, there are several other types that may produce easier for you in your situation and area.
Essentially, the plants must have at least six hours of full sun a day and must have excellent drainage (one reference even suggests adding 50% large gravel and/or small round rocks to the planting medium to facilitate drainage), plant in raised beds, and try to observe an average 1" per week of water. Although I didn't see it on any of the sites I visited, I would still assume that when watering by hand, water applied directly to the soil and avoiding the leaves as much as possible is preferable to keep down fungal and virus issues. In addition, lavender apparently appreciates as much natural heat i.e.: summer temps, as you can give it although some simple care on well established plants should carry them through all but the most severe winters.
There is an abundance of sites available on the internet by using simple search terms such as "types of soil for lavender" "growing lavender" and so on.
Hope this helps with your plant issue.