"You look well" was definitely code for "you've gained weigh" for my nan, all my aunties and my Mum.
I knew this perfectly plainly from childhood as after whichever poor sod had left, they'd mention the half stone they'd think she'd put on. Merseyside and the North West family.
The exception was an emphatic ,"oooh, don't you look well!" which meant you have a tan.
I met a woman last week I'd not seen in 3 years. She's in her 80s. She said "you're looking well," and I said, "well, I have gained about a stone," and she said "yes, but you are still full of smiles," which is about as positive as that phrase gets around here.
"You look good/great/wonderful" meant they approved of your looks.
If a bloke said it, I bet it means you just loked nice. The crazy gradations of nuance and hidden criticism seemed to be a a matriarchal thing, at least in my experience.