I'm curious whether, if JJ's medication was used to sedate both children, JJ might have developed a greater tolerance for the drug since he'd had it many times before (sporadically, it seems, based on Lori's needs rather than his own). So, if Tylee was given a dose that either killed her or sedated her sufficiently to allow subsequent acts (e.g. suffocation or drowning in the bathtub) to occur without her waking and struggling against her killers, that same dose might not sufficiently sedate JJ to accomplish the same thing. So, JJ might possibly have become awakened when his killers began suffocating or drowning him, causing him and them to bump into things - thus creating a need for LVD to explain away those sounds as JJ crawling around on top of the cupboards and knocking the picture of Jesus off the refrigerator.