Hiya

Because you're looking at them every day you won't notice the size change ( a bit like how it is with kids

)
Pot bellied pigs are slower growing anyway, I wouldn't worry overly much at the minute

As long as they are healthy and eating well try not to panic.
If you don't want to pick them up (I put my small pigs & piglets in one of the blue woven Ikea bags and hang on a luggage scale to weigh them

) You could measure behind their front legs and their length, there's a calculation to figure out approx weight (heart girth x heart girth x length - all measured in meters so you'd have 0.something

muliply that answer by 69.3 and you've got their weight in Kg) or you could just take their photo in the same spot every time (against a gate or something of fixed size) to give you a visual reference.
HTH
Karen