I Have 2 Puppies (10wks) Frm One Of My Older Dgs And Both Just Died 2 Dys Apart Of Same Symptoms?

Symptoms: Stomach sun-king in, dullness in face, not eating. First pup i found laying in the grass weak and couldn’t move but still breathing but was unresponsive like it was in shok or something, i moved it and tried to get it to stand but it wouldn’t its head just fell bck lifleless and motionless, it could not even move a limb, did not make a sound or nothing, 30mins later it died, then i discovered blood all around its anal side. 2 dys later the other died of same symptoms. I called my vet office and describesd what happnd to them cause i have 3 older dogs one of which is their mother cause it seemed like parvo to me after reading bout it. the vet tech said it might be worms also. I had no idea worms killed pups like that? I realized that they were dewormed but only for roundwroms with a over the counter wormer and just found out it was expired since June. Their mother and my other 2 dgs were also only dewormed for roundworms a long time ago but were given all their 3 sets of shots as a puppy and are current on rabies shots.and one of them usually get his booster every yr as he is 4yrs and the mother and other one just turned 2. Do i need to get a booster shot for them in case of parvo? any idea what might have happened? She has had a litter b4 but they all survived. also she did breast feed them still when they were about 7-8wks old.I have had dogs for the past 12yr and never had one die on me am just so paraniod now. Someone was goin to take them and also take them to the vet thats why i had not done so, so it was not that i just neglected them. I don’t know what could have happnd. but thinkin bout it could have been worms since it lives in them and could have been causing issue that i did not know. But they just seemed fine to me and symptoms only showed for a day and next day it was dead.