[ye-olde-sysrq]

It could be that this is showing drying up of future (or near-term future) possibilities that this is a high-growth company. If investors were predicting they'd be growing at a certain rate (and a higher rate commands an exponentially higher P/E multiple) and now that rate is lower or even flat (or even shrinking), then that's going to be a big drop as a "small" movement on the X axis (of growth rate) produces a much larger movement down the Y-axis since it's an exponential relationship.

TLDR if investors see this as a "party's over" signal and most of the big/easy growth is behind, they're going to flee.