Key Takeaways:Nayuki slipped into the red in the first half of the year, as its margins plunged on sharply lower sales per store amid growing consumer cautionThe company’s stock is valued far lower than its more aggressive peers that have far bigger store networks using a franchise business modelBy Doug Young The bitter taste of losses is brewing in China’s overheated bubble tea economy, where Nayuki Holdings Ltd. (OTC: NYKHF) has become one of the first major players to slip into the red. Nayuki’s latest earnings report is filled with trouble signs reflecting the industry’s current state of c…