A mystery BN disappearance.

I notice suddenly today there's much fewer of them suddenly. The other day I saw a bunch hanging on the glass..I figured oh well, they must be hiding.
I removed all the hiding places and still not many left.
I can't even see any dead babies in there.

There's no other fish in the tank with them, just a pleco family tank. I've been getting them ready ( or at least some of them to be shipped off). Just to make sure they'd be ready for shipping, today I tested the water and the parameters are perfect.

What happened?...Did the parents turn on their babies because that's the only explaination I seem to have left.

I'm running two filters behind a tank divider in that tank and I have not yet checked.
So far this has been the most effective way of keeping baby plecos away from filters.

I don't think so?...I've been giving them slices of zucchini, but I was gone over the weekend.
Whatever happened effected all the smaller babies. The larger ones are all still here.

No, they were from different litters/batches. 3 of the 4 left were from the June batch.
I had intended to give them all away, I ended up giving away 22 of them and 3 popped up in the tank later on.

I'm wondering if we had a cold snap here over the weekend.
I know this place is bad about temperature regulation sometimes.