Why is my Witbier OG low?

Just finished my second AG batch yesterday - a Witbier recipe from Midwest. I went for the added challenge of doing a protien rest as well. It all seemed ok, but the OG came in low. I am batch sparging in an Igloo 10gal with circle hose braid. Any ideas on what happened? Will it be an obvious or subtle difference when tasting? Looking forward to it at any rate, just want some tuning advice.

Actual OG 1.037
Target 1.042-1.046

Recipe
5lb domestic pilsner
3lb white wheat
1lb unmalted wheat
0.5lb Carapils

1oz Hallertau 60min
1oz Liberty 2min
1tbl coriander 10min
0.5oz bitter orange 10min
Wyeast 3944

8.6qt @ 135F for target of 122F 25min
(actual was 127F due to preheated tun)
5.4qt @ 200F for 152 (152 actual, dropped to 150.5 at 45 min)
7.2qt @ 200F for 170 mash out
11.2qt @ 170F sparge

Boiled 60 min and ended up with a hair under the 5.5 gallons I was shooting for.

how'd you do with your first AG batch? it usually takes a few batches to dial in efficiency with a given system... i'd say you're pretty darn close, have you calculated the efficiency? there is a good sticky in this forum with tips for maximizing efficiency with batch sparging. i would definitely recommend browsing through it.

My first batch went ok except that I boiled a bit too hard and came out at about 5 gallons for a 5.5gal target. I could have topped it up, but the calibration mark I put on the carboy at 5.5gal was also at 5 gallons. Must have been drinking when I did that. So, a little syrupy but still drinkable.

I'll check out that efficiency page.