I do think the one with the bright orange/red tail looks a like she might be. The other 2 do not look pregnant, but there is a good chance that they are since they were being kept with males. Keep an eye on them and see if they start to get bigger. After being in contact with a male, female guppies can store sperm for up to 3 months. So, they may all have mated and time will tell if they are pregnant or not.
Two roads diverged in a yellow wood, but thankfully they both led to fish stores.