Avengard Pils was 5.2 at 34C/93F - I was in a hurry, so it was a bit warm still after mashing at 151F for 10 minutes.
Hmm, that is low for a base malt, but the temperature was too high. That was a test mash, you had the time to let it cool. The other caution is that you do need to go much longer than 10 minutes. A half hour isn't unreasonable.
I've noted that initially low pH's tend to rise and initially high pH's tend to fall during the mashing period. They happen to point to a pH of around 5.4. It's a weird phenomena that I've also shared with AJ DeLange to see if we can figure out what's going on. Its probably something to do with the phosphate buffering system in malt.