I’ve set up my relays via Damus which I suspect is R+ RW?

Ah... Yes. I think Damus is treating all of them as both read and write. There is no way to change which is read vs write within their interface at this time. You can specify which is read vs write in Nostur. Just make sure to also use the "announce" option, so other clients will see which relays you want to use for each. Not sure whether Damus will respect the read/write flags or just treat them all as both anyway, though.