Hi Salad
I don’t think that it’s anything to worry about. When I feel a pregnant tummy sometimes it is very easy to feel the limbs, hands, feet, head etc. And yet with other tummies it can be quite difficult to know what you are feeling.
Measuring small for dates could be an indicator for low fluid levels but it could also indicate that your baby has changed position, or even that you have put a little extra weight on around your tummy and is therefore not a good indicator of your fluid levels.
One reason that you could be finding it easier to feel hands and feet etc is that you are more ‘tuned in’ to know what you are feeling. During your first pregnancy you would have felt your tummy a number of times and trying to work out what you were feeling. With this pregnancy you have already had some practice so to speak and therefore you are finding it eaiser to identify the parts you are feeling.