Hi everyone. Bit of an odd one but I don't really know what to do.

One of my little Tonks Bella is not cleaning her bottom properly - I can see how it is happening - when she sits down to clean herself, her tail covers up the top part of her bottom as she sits all crooked and she keeps missing it lol but she is sometimes a tiny bit squiffy and I don't know whether I should use some cottom wool to help her. My other little kitten Misty is fine but Bella just doesn't seem to get it right lol. She is always cleaning herself and is very clean cat but she just keeps missing a bit.

Any advice would be greatfully received.
Thanks