Ah yes, female guppies from the store are often already gravid I'm afraid. It's always a risk with female livebearers. Not unusual for a male to have jumped into the female tank at the store or
at the fish farm, or if the fry aren't separated by sex quickly enough, they can get knocked up way too young.
Unfortunately, your tank is really too small for guppies, but especially for breeding guppies. Females can store sperm, so even with no male around, they can keep churning out fry every month for a year or more. Chances that the other is also carrying sperm packets are also high. One was, so it's likely both have been near a male.
Five gallons isn't a lot of water volume, so it can turn toxic quickly, and it's soon going to be overcrowded with the two adult females and four rapidly growing fry, plus however many fry are born in the coming months. Guppies often have 30-40 fry per month, and they've even dropped as many as 200 in a batch... you need extra tanks for fry, and to separate fry by sex, and you also need somewhere willing to take fry. Most big box chain fish stores won't take livebearer fry bred by home hobbyists since the risk of disease is high, so you'll need to approach privately owned LFS to see if any are willing to take them. My LFS takes in my livebearer young, but even then, I have to grow them out until they're three months old so they're old enough not to get sucked into the store filtration system, and old enough to sell.
Sad as it is, unless you can find a store willing to take them, or sell/give away guppy fry yourself privately, and get a larger tank for the adults (a ten gallon for 4-5 adult guppies plus shrimp and snails could work) and use the five gallon as a grow out tank for fry, you might need to return or rehome the guppies once they're well
It's a cute little tank, it could work as solely a shrimp and snail tank, or it could work for a single betta fish if designed right, but not much else I'm afraid. For the future, a tank that is longer than it is tall is better for fish. They appreciate the horizontal swimming space since they don't tend to go up and down as much as they like to go from side to side, so these tall tanks are cute, but less ideal for fish.
I'm really sorry, I hate breaking this sort of news
Or telling people they need to get rid of fish. You could probably rig a temporary tank for the fry using a plastic tote like this;
View attachment 116547
With a heater (and heater guard so you don't melt the plastic!) and a sponge filter, it can work brilliantly as a temporary hospital, breeding, or grow out tank. Not exactly pretty, but it gets the job done! Also more water volume means the toxins produced by fish waste (ammonia and nitrites) are more diluted, keeping water levels more stable and giving you more time to react and do water changes before the levels become dangerous.
More than happy to help you figure out what you want to do next, that tank would fantastic to aquascape as a shrimp tank, shrimp don't mind and will use vertical space if you scape it right, and a colony of red cherry shrimp or blue dreams are endlessly entertaining, and pretty. Or a nice betta perhaps, they have some personality! Some of them don't get on with shrimp and will eat them, but some ignore shrimp completely, comes down to the individual bettas personality.
