Say a red team gym with 7000 Prestige has three Pokemon defending it, a 500 CP Golbat, a 700 CP Pinser, and a 1500 CP Snorlax.
As a blue team member you attack the gym and defeat the Golbat and the Pinser but the Snorlax takes out all your remaining Pokemon.
Will the gyms prestige go up, down, or be unchanged?