I'm guessing the bath has moved at that point then. Are the feet screwed to the floor? Usually baths are fixed to the wall as well but other jobs I have visited before similar to your case I have found that they are not. If you can move the bath closer to the wall and screw the feet to the floor...
That is quite a gap there. If the bath can be pushed back to the wall that would be the ideal solution. However I'm assuming the wall is not quite straight so that's why bath won't go back to wall in certain places. For a cheaper option I would run a bead of silicone then let that go off for 24...
