How Apple went from a $1 trillion company to losing over 20% of its share price

Apple announced a multi-billion dollar loss in projected revenue and their stock plunged. Some analysts think iPhone demand has slowed, especially for the iPhone XR and iPhone XS. Apple's CEO Tim Cook blamed slowing sales in China and the battery replacement program. Apple also announced that they would no longer report the iPhone sales numbers. What's going on with Apple's iPhone?