@TheGrog I think that is right about the clay soil, probably combined with our heat (I'm in Arlington). Mine all survive and produced a reasonable yield, but they definitely look a bit rough mid-summer and just sort of stop growing and get a little yellow around the edges.
But, like I said, they do okay and produce fruit. The ones that are doing the best for me get about 4 hours of sun and nothing pats probably 1pm, so that helps them not overheat, and they are in rich amended soil with a good layer of wood mulch. Plus the neighbors downspouts are only about 10 feet away and wash down toward them so at times they are almost in a rain garden. I keep a couple gooseberries in a half shade rain garden (also no real afternoon sun), and they do a little better during the hottest part of the summer. I have 2 that are in more clay and don't get as much moisture and they definitely suffer more in the heat.
So for us on the southern edge of where they might grow, I think part shade and good rich soil and making sure they get enough water really helps. I haven't had any real problems with powdery mildew, so hopefully that continues.
Of the ones I grow, the Belaruskaja is by far my favorite to eat fresh. I also have Minaj Smyriou and Titania, with Minaj really growing strongly and being the heaviest producer, but not nearly as good for fresh eating. I think I'll also add some Ben Sarek since I had some from a farmers market in NY and they were quite good and I like the fact that the plants are compact.