Early pregnancy loss. Was missing!

Hello i am 37 year old female. have one baby of 4 year. had naturally conceived for 2nd baby. i was in my first trimester. At 5w 2d my baby heartbeat was detected but not enough to get recorded. At 6w 2d my baby heartbeat was only 94bpm. At 6w 2d i had very slight spotting and hence was asked to repeat the scan. heartbeat was 94 and dr put me on susten 300 twice a day. bleeding stopped and was happy that everything was taken care of. now i repeated the scan at 7w 4d and no cardiac activity was seen. how can this happen. ps- i had consumed some quantity of hing peda accidentally for gas issues for 2 days before i had slight spotting. however with susten spotting had stopped completely and after 10 days when i went for scan foetus was seen but cardiac activity was missing