Hi everyone! I have two thompson seedless grape vines, both on the eastern side of my house.
They are growing on opposite sides of a pergola and get sun at opposite times of time (ie: the one that is 'dying' gets more sun in the mornings and the other one gets more sun in the evenings as our house's shadow doesn't fall on it). We are trying to get them to grow up on top of the pergola and shade our deck in a few years.

They're both about 7 feet tall, but recently the healthy vine has had a nice little growth spurt and is doing a lot better now.

I recently found two achemon sphinx caterpillars on the one that is dying, and quickly destroyed them. I've checked every day and cannot see anymore. I have BT and will be spraying that soon.

Other than that, I water them at the same time of day and for the same length of time but the dying vine just looks like it's burnt out.

The photos don't directly match any 'diseases' I can find online. The leaves just look like they're really dry and crackly. They will fall off sometimes, like an autumn tree loses it's leaves. And recently too one of the healthier new 'stems' that popped up has gotten some brown spots on it (will attach another image if possible).

The dying vine has two separate little grape bundles growing from it that look like they are completely healthy.

Other than the burnt look, there are these tiny little black dots on some of the leaves as well.

The other vine is doing tremendously well. I'm watering them a lot more than I did last year and wow!- the healthy vine has huge leaves on it! So I just don't know why this other vine has such dried out small leaves on it.

I would appreciate ANY HELP or advice!

Should I be watering differently?!

If it makes any difference, these are in their own "planting pots" or like, wooden boxes with dirt in them adjacent to our deck. But the dying vine is about 6 feet away from a pretty large chinese ash tree. I doubt it'd mean anything but just in case...