Now it is obvious that the problem of Newcastle is a psychological one primarily caused by their exit from the European championship. The depreciation was too rapid and continuous. Losing 1:3 to Nottingham Forest in their is what will not happen when they were playing with enthusiasm. Not only that, Leeds United also beat them 1:0 which is enough reason to conclude that Newcastle has become a shadow of itself.
What they need now is the introduction of new faces in the team and a possible change of coach to reinstate the winning psychology in them because if they continue the way they are going, they might be relegated.
You mentioned a few examples for bad games that Newcastle played and then there elimination from the Champions League and the Europa League at the same time. If the games against Nottingham Forest was an exception, everything would still be alright. But Newcastle is going straight down the table with high speed. That is what makes people who support the club be concerned. It's not clear whether they can fix all the issues within a short period of time and get the chance to qualify for the Champions League for next season again. At the moment it looks as if they won't have a chance to compete for the top 4.