I recently turned in a beer for a local competition. Overall I received pretty good scores, but 2 of the judges left the "grassy" remark as part of their evaluation.
I'm thinking this is due to dry hopping, but I'm open to suggestions as to what else can cause this. In the past I definitely got this flavor when dry hopping cold. Here is my general strategy to dry hopping.
1. Rack from primary to secondary
2. Dry hop secondary for 2 days (or so) at ~ 68F
3. Remove dry hop mesh container
4. Cold crash and fine with gelatin (1-2 days, sometimes longer)
5. Rack to the keg and carb.
Here are some ways that "grassiness" can make its way into your beer.
1) Hop variety - Some hops give more of a grasssy note to the beer. Trying a different variety might help.
2) Old malt and/or hops. Some malts will take on a grassy note if they are stored too long or improperly (too high a storage temp or unsealed at a high humidity level. Grain that is exposed to really high humidity tends to go slack (stale) and will have a mushy consistency when you chew some up. I always do a "bite test" on grains that have been around for a long time to see if they are still crunchy and have a good malt flavor. With hops, even if they don't smell cheesy after long storage, they might be grassy and you should be able to smell the grassiness. Using really fresh ingredients, if you can get them will alleviate this issue.
3) Using way too much hops during the boil. Try a different variety with higher alpha acids as your bittering addition so that you can use less in the boil.
4) Dry hopping for too long a time. It appears that you are OK on this issue from what you stated. Maybe a different variety of dry hops will help. I normally dry hop for no longer than 5 days (sometimes only 3 days) in the secondary at 68-70 degrees, then rack the beer to the keg, crash it and carbonate it. I use in in-line screen (that I got from Grainger) to capture any hop particles that are sucked out of the secondary by the racking cane before the beer hits the keg. FYI, I don't fine most of my beers (only lagers like Helles of Octoberfest). Sitting in the secondary for 5 days usually clears them even at room temperature. There may still be some yeast that falls out in the keg after crashing but after the first glass or two the beer will clear up when serving.
Hope this helps