I would guess they were drugged.
If they were murdered in a cultural punishment, that would be extremely odd. There is the strong idea in cultural islamic punishment murders that the condemned should be shown "mercy" and allowed to speak the shahaddah, pray, and/ or recite the koran as they experience their final moments.
This is because of the concept of repentance, and is seen as being especially merciful to the condemned. If the words of the shahaddah and prayer are on their lips as their final words/ thoughts, it is believed Allah will be merciful and grant forgiveness.
Taping them bound together facing one another is another way, IMO, that they were made to "face" what they had done together, their rebellious behavior, and have a chance to embrace and pray, comfort one another in their deaths, and express repentance, as they die. A way for them to save their souls.
This may seem very strange to some, but to me, the method of their deaths as ritual cultural murders indicates someone was trying to make their murders "easy" for them to bear. Perhaps signalling to the family that it was necessary to punish the girls with death, but that the murderers made it as merciful and easy as possible, and for them to be able to repent at the end and save their souls.
I am not surprised their mouths were not taped shut, or their arms restrained. Islamic ritual murder is frequently justified in that culture as necessary, but merciful and honorable. They are being helped from committing further sin, rebellion, dishonor. Essentially, "cleansed" by death.
Additionally, death punishment water drownings are viewed as a “soft” and easy form of death, and "merciful". And "cleaner." As in, showing a perverse kind of mercy to poor wayward young females by drowning them, which is less violent than other more violent methods of murder/ execution, such as stabbing, etc.
It may seem very hard to understand, for westerners. Most western perceptions would be that that binding them facing together is additionally unspeakably cruel and sadistic, revenge-like. Murder was bad enough, but binding them facing each other ups the sadism factor.
Toxicology results will take about 6 weeks, but I'd be really surprised if they test positive for anything. That would, IMO, be highly unusual, whether they were murdered, or committed a bizarre suicide.
I know some think this is a double suicide, but I just don't see one single thing that persuades me that this could be suicide. IMO, this has all the hallmarks of a ritual cultural murder.
