This morning Bim when i lifted Bims tail she had it clamped quite firmly down and it went to the left when i did lift it. She was absolutely fine under the saddle and was actually really keen to get on with some schooling now the ground is a bit softer after the storms but just was noticably stiff in her tail. What is this an indicator of?? Over swishing for the removal of flies perhaps?? Or something more serious??