US05, oh boy, let's talk.
I use this yeast as my house yeast, and my best friend does as well. Probably 80-100 batches between us have been brewed with 05. I'll go through my standard procedure first, then we'll talk about when I deviate. Normally I chill to 60-62F. Rehydrate in 90-100F water, and ferment at 62F until it slows down. Once fermentation slows, I'll raise the temp over a couple days up to 68-70 until activity stops. Beers brewed as such are super clean, and attenuate very well. Between the cool pitching temp, and cool fermenting temp, it does work a little slowly, but the warmer temps near the end of fermentation help the yeast attenuate.
-I've found if I pitch over 70, I get some slight phenols.
-I've found if I pitch over 70, and don't immediately chill the wort down to <68*, I get phenols
-If the temperature fluctuates more than 3-4* on a daily basis I get some phenols
Aside from that, it's a rock solid yeast. It's definitely slower to flocculate than WLP001/1056, but I also find it a little bit more attenuative, so that makes sense. I don't pick up the peach ester others get. Since I have a fermentation fridge, this yeast is a no-brainier. I have a 1* window set in my temp controller, so it's just point and shoot with this yeast. It's a great yeast. I've had three beers score in the 40s in competitions using it (44 being the highest.)
Are your temps swinging thought the day? Are you pitching warm?