Catch up on today's top five analyst downgrades with this list compiled by The Fly: 1. Costco (COST) downgraded to Market Perform from Outperform at Wells Fargo with analyst Edward Kelly saying while Costco remains one of the highest quality companies within consumer and its near-term results should be positive, "this may be as good as it gets." 2. Dunkin' Brands (DNKN) downgraded to Sector Perform from Outperform at RBC Capital with analyst David Palmer saying while sales have accelerated sequentially, the current valuation of 22-times his expected FY20 earnings "reflects much of the turnaround." 3. Valvoline (VVV) downgraded to Underweight from Neutral at JPMorgan with analyst Jeffrey Zekauskas saying industry trade publication National Oil and Lube New is reporting that Amazon (AMZN) has launched its first private label motor oil called AmazonBasics Full Synthetic Motor Oil. 4. DDR Corp. (DDR) downgraded to Neutral from Buy at Citi. 5. Tandem Diabetes (TNDM) downgraded to Neutral from Outperform at Baird with analyst Jeff Johnson saying at some point valuation will matter, so he moved to the sidelines. This list is just a portion of The Fly's full analyst coverage. To see The Fly's full Street Research coverage, click here.