It could also be sparse data. If you have only a couple houses listed at 3 bedrooms, any change could just be noise. Maybe the more expensive house this month has better views, more upgrades, is newer, better location.
These are list prices, not sale prices. Sale prices are not completely accurate if they hide closing costs or other incentives.
I think San Diego Market Monitor and ocrenter’s lists are the most accurate, because they show the prices of the *same* house over time.