Bathtub separating from wall
Appearance of this crack has nothing to do with foundation; it is something that you can see in many bathrooms. First check if both wall and bathtub are vertical, if they are not this crack will most likely appear from time to time (every year or so).Now, you can do one of two things: You can use silicone to glue it together. Keep in mind that silicone (or similar material) should be replaced every 6-12 months you will know when to change because black dots will start to appear. Another thing you can do is that you can put a rubber band and just glue it to both sides. Now this solution is more permanent (you don't need to change it so often) but if you ask me it's not that pretty. Now, foundation....since you did all that work maybe (if possible) you should give your house couple of months or a year to settle before you start doing anything.