Has more water in it
The softness of poo usually depends on the water in it.
Some people have soft poo as their "normal", but a change from formed poo to "too soft" poo is likely a problem. Poo that travels too quickly through the intestines will still have too much water in it. Poo mixed with undigested sugars (excess fruits, juice) will hold on to much water. A doctor can check for infections like giardia