Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of property management software specialist RealPage, (NASDAQ:RP) plunged 20% today after its preliminary Q2 results disappointed Wall Street.

So what: RealPage shares have rallied in recent months on optimism over accelerating growth, but today's downbeat Q2 view is forcing Mr. Market to quickly sober up. In fact, management blamed the miss on weak marketing spending from owners due to low vacancy and resident turnover rates, triggering plenty of concern among analysts over the company's near-term operating environment. 

Now what: Management now sees Q2 adjusted revenue of $93.8 million to $94.8 million, well below its prior view of $106 million to $108 million. "We believe lower than expected revenue driven by weakness in leasing velocity and marketing products was primarily responsible for our revenue and profit miss," said Chairman and CEO Steve Winn. "We intend to stay the course on our sales expansion investments and complete the rollout of the richest product development backlog in our history." When you couple the headwinds facing RealPage with its 20-plus forward P/E, however, I'd hold out for a wider margin of safety before buying into that turnaround talk.