RIS - Bad steep?

[SlugTrap]

I just brewed my first Russian Imperial Stout.
Typically for the style, it had all sorts of specialty grains for steeping.
When the time came, I measured an OG that was very low and very unexpected - something like 1.085 instead of 1.100.

Since extract is more or less straight sugar and I didn't lose any wort (no leaf hops) the only thing I can figure is I got terrible utilization off of the specialty grains, which did (or should have) contributed significantly to OG according to BeerSmith.

Any ideas why this would have happened?
Or could it be something else I haven't thought of?

[Drum]

Did you mash the speciality grain with some base malt or just steep them all together? I learned the hard way that not all grains will self convert their starch to sugars on their own. Im guessing you had some flaked barley in there as its a stout? That would change your OG depending on whether its mashed or steeped. 

Also, what was the temp of the hydrometer sample? Did you correct for temp?.   Sorry if i sound like a cranky teacher. Im just thinking aloud

[SlugTrap]

Thanks for the input, folks.

Yes, they were all dark grains; no, I didn't add anything diastatic - that's two answers right there.

I measure OG right before I pitched, so the wort would've been about 25C. What should it be? Haven't heard of temp as a factor...

[beerfly]

It will just be down to the grains
Because of the way they are malted most crystal grains have already converted themselves so you will get some sugar out of them but the darker ones wont have and the malting process will have killed of the enzymes.  Flaked grains dont really convert even in a full mash

hydrometer temp correction for 5c .001 so not a factor