by the look of it this pic it does'nt really determine if they are pregnant or not, it is quite common for females to have this spot anyway as it is one of the ways to determine its sex
the good news is that they are in with males and male guppy are always at it and theres no chance of the females saying no.
you need to give them atleast another week to observe the swelling and gravid spot getting bigger and darker, when this happens they will be pregnant
when people first get female guppies the urge to know if they are pergnant is really high, due to the fact that they breed so quick and are easy to raise from fry
lovely photos by the way