What was wrong with my pup?

My puppy died. She was sick I need to know what it was. she was sick for about 5 days. at first it was that she wasnt eating. but she was drinking. she wasnt lazy she still played outside and wanted to be outside NOTE: she wasnt wondering off to die. but she still wanted to eat by the i think i noticed she was sick on the third day she was very skinny still drinking not eating then her stool was like water no bad deathly smell 5th day it was pink pastey gooey then some clear vomit with alittle bit of foam 5th day wouldnt do anything stayed in her box would either lay down or sit she did both she got up once to use the bathroom but ended up pooping the second she got up an dripped til she found a spot to go by that time she was pretty much done. it was redish brown a stunk almost the dead smell gums on 5th day where whitish grey dehydrated and also on the 5th day i noticed she was coughing and sounded congested that night she died. i remember she was like gasping for air the minute she died she pooped blood everywhere like we felt her heart stop and there it was i remember it was hard to keep her warm the 5th day and semi hard to keep her warm the 4th night