Aquariums: what’s wrong with my guppies? :(

So I started my first freshwater around 2/3 months ago. Set it up empty and let it cycle for 3 weeks until the water was correct then we added shrimp. 2 weeks later when the shrimp were thriving and plants were growing we got 4 guppies to start with. I floated the bag, I slow drip acclimated them, and they seemed to be doing well. Within about a week 2 of them had died. I’m pretty sure one had swim bladder from the store because he looked pretty immobile and puffed up when he got home. I isolated him, gave him peas and swim bladder treatment but it was too late. The other one was just found dead so not sure how that happened.

We went back to the store and asked them and they said they never have problem with swim bladder or fish dying. They tested the water and said it was fine. We got 5 more guppies and this is the last of the 5. I’ve just been slowly finding them all dead. One had a white string coming out of its bottom so I think it was a parasite.

Two fish from the original batch are surviving and look heathy; this is the last fish from the second batch. Obviously looks very haggard and isn’t moving a lot but occasionally he swims around like everything’s fine.

What am i doing wrong? I feel so bad. The shrimp are thriving and having babies but the guppies are suffering 🙁