Any bugs, creepy crawlies, sticky lumps, white fluffy patches or anything on the poorly one? Pics would be good
HI, bay are pretty easy and pest and disease free. I had two standards too and lost one of them.I would put down to to the very wet weather. They do not like soggy conditions. I do shed some leaves in the autumn so I suggest you perservere and it will perkup in the spring.
I wonder if one is sitting in a colder windier place than its brother? Our golden one outside the back door got like this, I cut it back to ground level preparatory to removing it, and it shot up with new stems and has - so far - been great since. maybe a hard prune might help yours too?