Things that are noticeable and more apparent on 2nd viewing (spoilers)

On second viewing, with the knowledge that Lydia is guilty of infidelity with Jarvis, seemingly innocuous and regular scenes and behaviours have different meanings and are more noticeable between the three main characters.

Jarvis is noticeably nervous in a few scenes. There's a scene after about half an hour where Kyle and Jarvis are outside smoking and Kyle is nervously tapping his leg. He then goes on to talk about people cheating all the time and then curtails his conversation when he talks about Kyle doing a "terrible thing" as his mind is on the "terrible thing" that he has done.

Lydia comes home drunk and asks Kyle if he has ever cheated on her. This now appears to come from her own guilt. She then goes on to say that "we are all human, we all make mistakes" as a way to rationalize it.

In the scene where Lydia complains that her "fanny is on fire" there's a good likelihood that this is the symptoms of chlamidia, and not the jalfrezi on Kyle's fingers, as pain during sex is one of the symptoms.