Declining economic activity and a serious drop in existing home sales opened the door for housing stocks to take a beating Monday.

Tech stocks in general were hit hard as the Nasdaq saw a sell off but every single one of the HW 30 except for Bank of America (BAC) closed down Monday.

Zillow (Z) and Trulia (TRLA) – being housing and tech – seemed to take the brunt of it, with Trulia down 4.63% on the day and Zillow down 4.02%.

The National Association of Realtors reported on Monday that sales of existing homes dropped 1.8% in August, blaming the drop on all-cash investors sales retreating.

However, Bill McBride at Calculated Risk quotes housing economist Tom Lawler who questioned that excuse, saying:

In the first quarter of 2014 the NAR survey suggested that the all-cash share of home sales was noticeably higher than in the first quarter of 2013, even though other reports (based on property records) and local realtor/MLS reports suggested otherwise. While these other reports do suggest that the all-cash share of sales over the last few months is down significantly from a year ago, they don’t suggest that the all-cash share plunged in August relative to July. The survey’s distressed-sales share also looks way too low.

Tuesday morning will see the Federal Housing Finance Agency’s house price index released at 9 a.m. ET, so it will be interesting to see if the markets react. Because the data will be for July, it doesn’t seem likely.