Southern China is more or less a jungle (selva) and these shorter plants hate full sun especially when juvinile same as Rhapis sp. Try moving it into a shady spot. I've had trouble with some smaller Dypsis species for the same reason. They look sad in full sun as they are adapted to growing in a shady jungle. Even Archontophoenix juviniles hate full sun. They'll tolerate it as they get older but hate wind. In the jungle other trees slow the wind. Now that my Archontos are bigger they get leaf burn and I have high relative humidity as I'm in sight of San Francisco Bay.
I'm interested in your S. sanconas. IMHO it is the most beautiful of the genus. S. romanzoffianum is homely in conparison. They are about as hardy aren't they? I suspect sancona is a bit less tolerant of frost but not all that much. I get no frost in my garden.
The last hard frost was 89-90 when even freeway plants such as Myoprium had foliar damage. I grow and fruit bananas here. High elevation plants do great but I get few days over 80 so I lack the heat that makes some plants grow and as well my winter is rather wet especially this year our wettest since 98. Some plants just can't take cool and wet at the same time. But high elevation "tropicals" from 1000-2500 meters do great here such as Fuschias and Brugmansias. I have a few plants from the Brazilian highlands in the south of the country and they do very well here. The only real difference in their climate is they get rain all year long and at upper elevations they get more frost.
I'm also working on a desert garden in Palm Springs. I'm accumulating plants for there but I cover them in winter to keep them dry. Nannerrhops dies here from drowning otherwise.