Apple’s stock fell 5% today, reaching its lowest level in nearly four months, after key suppliers cut their forecasts citing reduced orders from a major customer.

Lumentum Holdings, a supplier for 3D sensors used in Apple’s Face ID technology, and screen maker Japan Display, both lowered their outlooks because of weaker demand. Suppliers don’t tend to name major customers in their reports, but analysts have concluded that the two companies revised their numbers based on iPhone sales.

Wall Street typically monitors Apple’s supply chain as a bellwether of demand for its products. One analyst, Longbow Research, conducted spot checks with Taiwanese suppliers late last week and noted a 20-30% drop in orders related to the Cupertino tech giant’s newly introduced smartphones, the iPhone XR and XS MAX, and increases in orders for older models.

Smartphone assemblers Foxconn and Pegatron were told to halt plans for additional production lines dedicated to the iPhone XR, according to Japan’s Nikkei.

Analysts at JP Morgan cut their 12-month price target by $4 to $270, citing weakness in orders for the new iPhone XR, which hit the market last month. The iPhone XS and XS Max began selling in September, at prices that push the upper range for smartphones, starting at $1,000 for the XS model and reaching $1,500 for the fully loaded XS MAX with 512 gigabytes of storage.

When Apple reported its fourth-quarter results this month, it said it would no longer report unit sales for the iPhone, prompting worries among some investors because smartphones account for more than 60% of the company’s revenue. The company said it reflected a strategic shift toward services and away from hardware revenue. CEO Tim Cook also said the company may fall short of Wall Street sales predictions for the important holiday period.