I'm a little surprised what caused Tottenham to experience a decline in performance, losing 2-1 to Newcastle was really beyond prediction. I bet for them in this match but it's really unlucky. MU and Chelsea's points are getting closer to them, there is a possibility that their position will be shifted if they continue to lose.
Tottenham should have been able to beat Newcastle but maybe there was a movement that made Tottenham's defense weak and read by the coach from Newcastle so they took advantage of that to score the second goal, Newcastle had not many chances but they managed to take advantage of it and get a win against a great club like Tottenham.
Conte is trying a new scheme and for 2 matches they have done the same scheme and formation but this failed.
The 3-5-2 formation is not very good for them and it is better to maximize the 3-4-2-1 and focus on Kane being a pure striker.
Seeing this match with their new formation it is clear that this is not going well, actually worsening their performance in midfield and attack.
Son doesn't really fit in there because he prefers to run from the middle of the field than wait in front.