Factual errors: The initial murder occurs during an solar eclipse, which must occur on a new moon. A couple days later, a full moon is shown. This would have to be two weeks later.
Errors made by characters (possibly deliberate errors by the filmmakers): During the solar eclipse everyone looks up at the eclipse without any eye protection, during a solar eclipse if you don't protect your eyes with something you cause retina damage
Factual errors: Alex clearly says that phosphine gas could be produced from crystal meth that was cut down by chloroform or ammonia. Phosphine would require a phosphorus compound to be present. I guess the writers originally meant phosgene, which has a misleading name, as it contains no phosphorus, but which could be readily metabolized from chloroform.