Last few beers didn't fully finish out ferment. Why?

I am a little puzzled on why my last few beers didn't fully finish out their ferment and wanted to see if anyone had some ideas. Here is a typical example of a brew.

• Mash rest is always around 150-151
• 1.065-1.085 beers
• Always use Wyeast yeast nutrient per recommended dose 10 minutes before end of boil
• Utilized Mr. Malty pitching calculator for all starters
• Used stir plate for all starters
• Typically build up the starter two to three days before and depending on size of starter will cool in fridge and decant on brew day and then let yeast and remaining wort come up to room temp before pitching
• Use .5 micron stone and 1 lpm of O2 for 1min (to get ~10ppm) before pitching yeast into 6 gallons of wort.
• WLP007 is the yeast I usually use
• Hold ferment at 67 degrees

Historically, I have never been able to hit the exact target FG (it's usually a little bit higher by a few points) I am now ending in the low to mid 20's and the beer just tastes too sweet for my liking. The only few things that have changed as of lately are:

• I have been trying to time my starter to be at end of high kraussen when I go to pitch it
• At the end of 60 minute rest I recirculate for 10-15 minutes with direct fire under my mash tun to get up to mid-high 160's before I start sparging.

What do you all do for "bigger" beers that maybe I have missed? Appreciate the insight.

P.S. I am also debating doing a blast of o2 10 hours after pitching per this thread where Chris White had talked about it.

Have you tried trash nutrient

Did you mean yeast nutrient? Yes, I forgot to add that. I always use Wyeast yeast nutrient.

What is your usual attenuation? Do you use a lot of roasted malts? Here is a basic equation I use to get myself in the ballpark of what my finish may be:

((OG(or predicted OG)-1)*(1-Yeast Attenuation)+1)

So say you start at 1.08 Assuming 75% Yeast Attenuation

.08*.25+1=1.02
If you had almost perfect attenuation with WLP007 you'd end up around 1.016 (assuming a highly fermentable wort)
This is very approximate, and doesn't take into account the fermentability of your wort. since you mash at a lower range, your fermentability should be quite high, although adjunct malts you add will affect this (crystal, aromatic, roasted).

You may like your result better switching to a higher attenuating yeast, but that will change the ester flavors that develop that you are used to. WLP007 is fairly high attenuating anyways and can (according to White Labs attenuate up to 80%). One beer I brewed I added honey 2 days into fermentation it was quitea high gravity beer, but the monosaccharide honey kind of kick-started the yeast again and I had great attenuation.

That's just what I understand of it, the wiser follow me perhaps, if they don't don't blame me.

I use WLP840 and 550 a lot, they attenuate very high. Most yeasts that have an average in the upper 70- to low 80 attenuation range are Belgian styles, high gravity yeast, champagne yeast, White has an American Ale I believe that ranges around 75-80