I have done a bit of everything. I started with some extraxt kits and moved to all grain using my own recipes. The off flavors I have had are usually an odd sweetness. Not bubblegum or juicy fruit type flavors. But the sweetness ages out after a month or two of conditioning. I think my issues may be related to fermentation temperature. I have pitched the yeast too hot in the past and I do not have anything to maintain proper temperatures other than a temperature controlled basement. I was also concerned about the water I use, assuming my mash ph was off or I didnt have the right mineral composition. I have also kept a few gallons of starsan for possibly too long though my ph meter read very, very low so it should have been okay. I plan on brewing another batch using brewtarget for assistance and recording every detail. Oh, and I dont have a wort chiller, so I have left my warm wort in a glass carboy inside a big plastic container filled with ice and water over night to cool. I had a rubber stopper on it to make sure nothing got into the wort, but I am not sure if that was a bad idea.
Basically I do not have all of the equipment I need to brew as efficiently as I should, so I am not sure where I may be going wrong.
Also, you should check out the water conversation I have been having in another forum regarding nassau county water. It seems there are several things that I should be concered with when brewing with long island water.