my 2 tortoise died in hibernation

I had 2 tortoise and i put them in hibernation the same way as before, they were 3 yrs old. i left them for an hour at room temperature but they did not stir,so i opened the box and the bigger one of the two had her head right out which i thought was strange and the little one was all closed up. there was no sign of life so i put them under their basking lamp and an hour later still nothing, then i noticed a trickle of blood from the bigger ones mouth so i picked her up and she just looked swollen everywhere and her shell was a strange colour and the little one just isnt doing anything but im sure she is dead too because there is a horrible smell from them both, im heart brocken because i dont know whats gone wrong. could they have froze to death because it was very cold one night and they were in the out house so i brought them inside and put them in an unheated room ,but what would make her bleed like that, they were very healthy when they went into hibernation please could you shed some light for me so that i will know in the future many thanks. Elaine