6 month old has gotten off sleep schedule

[kdm1984]

The little guy slept great through the night for most of his fifth month, but in the last two weeks, he's been up most nights except for one. We tried shortening his naps in the morning and afternoon, but that hasn't worked. We've also tried to allow him to correct it naturally (which he's been able to do before), but that hasn't worked, either.

Any ideas? Husband usually does overnight duties, but we gave them to paternal grandpa last night so we could have a break and sleep. LO didn't sleep for grandpa, either.