The son of the CO poisoned parents said his father made too much money to qualify for financial aid at Princeton University but not enough to live comfortably, which led to his motive. This is highly unlikely as Princeton has been rated as having the best financial aid in the country with over 50% of students on aid. Even families with annual incomes over $200,000 received aid.
Catherine tells the elderly woman's grandson that he won't be receiving anything from the insurance company. Not true - he'd be eligible for a refund of the money already paid out due to his grandmother's suicide.
They found out that the old lady was stoned on weed. The coroner says that THC doesn't have any cumulative effect. But THC gradually builds up in the fat from continuous smoking. The only way to clean it out is to stop smoking weed for at least 6 months.
Nick explains that the son of the CO poisoned parents was accepted to Princeton University by Early Action. This is not possible, because Princeton participates in an Early Decision admission program which is rarer than and different from Early Action admission.
When they show the pink woman, dead in bed, she can be seen visibly breathing.