Two of China’s largest fast fashion retailers, Temu and Shein, have warned US customers that they will face price increases from next week, as Donald Trump’s hefty tariffs on Chinese imports come into force. Both companies will be hit by new import levies, which will mean taxes of up to 145% being applied to Chinese goods. They will also suffer from Trump’s cancellation of the “de minimis” exemption, under which shipments worth less than $800 (£600) could be imported duty-free. That exemption was crucial in helping the low-cost retailers make…