Yeah, that’s a wooden harp, though. It swells the wood a bit. I can’t see why soaking would improve a plastic-combed harp, other than perhaps cleaning it a bit.
I don’t have any tips for the OP. What I sometimes will do with harps that feel a bit breathy to me is adjust the reed gaps if one or two reeds feel weird, but I don’t know what to do with a harp that overall feels like it’s leaky.