Two cities that have served as economic pillars for China’s southern province of Guangdong appear to be losing steam relative to their peers, prompting calls for stronger action to revive businesses.Tech hub Shenzhen and manufacturing centre Guangzhou reported gross domestic product growth of 5.1 and 3.8 per cent respectively in the period from January to June, both below the national average of 5.3 per cent.The simultaneous slowdown came as uncertainty grips the global supply chain and...