yeah- haven't paid much attention to fermentation temps- usually out it in the garage in the summer/spring/fall and start it indoors in the winter- I live in the mild PacNW so I have never been to concerned about it- usually not to hot around here
Behind sanitation the two most important aspects of brewing are fermentation temp control and yeast pitching. Use the search function here for 'swamp cooler', it's a cheap system many here use. All you need are a rubbermaid bucket and 2-liter bottles. Too high or even too low of fermentation temperature stresses the yeast and produces off flavors.
I usually end up putting more than enough yeast in- often times I brew a three gallon batch (less bottles- more varieties of beer in the fridge...)
Now for the other all important aspect of brewing, yeast pitching. Overpitching is generally frowned upon, but it should have nothing to do with your off flavor issues. I'm guessing your issues are fermentation derived.
I usually out a full pouch of yeast in a batch- enough yeast for 5 gallons rather than three- never thought that would harm it-
Reiterate from above, that shouldn't hurt anything. However over pitching (ie using too much yeast) in something like a Belgian, English, or Wit/Wheat would rob you of flavor/phenols. Conversely some brewers over pitch on purpose with say a mild English yeast to get a cleaner ferment for an American style ale. Make sense? In essence under pitching stresses the yeast creating off flavors, just like too high a fermentation temp does. While over pitching creates a cleaner beer with less phenolic/spice/flavor character.
I usually transfer to secondary after 3-5 days to get it off the lees- thinking that that might be the cause of some of the weird flavors
I suspect this is the other half if not a majority of your issue. Many brewers don't rack at all, kegging/bottling right from the primary. Commercial breweries routinely get away with moving the bier/dropping the yeast after a few days but homebrewers can't get away with this. Leave the next couple batches in primary for at least 2 weeks before racking. If that eliminates a lot of your issues you could reduce that number down to 10 days, but no less. All of this advice is dependent on the size/strength of bier you're making. I'm assuming your making 4.5-5.5% beers. Larger biers take longer, smaller biers can take slightly less time.
I usually leave in secondary for a long time- sometimes I rack again...
Thanks for all the comments! Merry Christmas!
DON'T RACK AGAIN, there is no need for it and good advice is don't do anything to your bier that it doesn't need... it's just asking for problems. Oxidation is very rare in homebrew but can be a problem if you're moving it too much. Since you're patient, let the bier sit in primary for a long time, then if you need to move it for a fermenter rack it... ONCE. Then bottle/keg.
Finally I first mentioned sanitation as the most important aspect of brewing. I'd say make sure you're good on that end, and I'm guessing you are as sanitation mishaps usually result in beer that continues to worsen with age, not get better.
Summary: Ferment in a swamp cooler and pay close attention to your fermentation temps as most ales ferment best in the mid 60s... consistency is important here. Next and VERY IMPORTANT, leave your beer in primary long enough for the yeast to clean up after themselves (14 days) (what they're doing after 4 or 5 days/after primary fermentation).
By moving the beer off the yeast too early you're stressing the remaining yeast as they attempt to clean up after themselves, creating off flavors! Pitch the correct amount of yeast unless you're brewing clean American ales all the time, even then it's still good advice. QUIT racking beer unnecessarily.
Good luck and Merry Christmas!
Also, I had heard the argument that the yeast in the cake will bind the hop oils to a certain extent, potentially not giving you quite as much bang for your buck (err, hop); not sure if anyone has rigorously tested it, but it's possible there is a small effect.
