The pH really shouldn't be an issue, it sounds like your plants were simply having the "Oh you changed my parameters!" melt before adapting. The vast majority of fish we keep are also extremely adaptable. For instance, I keep wild caught two-spot catfish that come from peat swamps, in a pH of 8.2 and dKH of over 5, and they're doing perfectly well. Naturally they probably don't experience anything over 6, and even that could be high for their natural environment.
Insofar as plants, they are also surprisingly adaptable at times, especially the ones you list. For example, I grow blyxa japonica like it's nobody's business, when on paper it likes low KH with a neutral to acidic pH.
I'd say give it time, rather than chasing parameters, let things settle in for a couple of months and see how it goes.