I'm having some trouble defeating him I got one of the three down before my party for killed >< I'm using potions when my pets get to about 60% health. Should I level them up more or change anything? (I might need to change things but I don't know what ><)

These are the pets I'm using (They are also my mission pets):

https://www.sylestia.com/view/pets/?petid=1013455 (proficiencies: 5 in strength 5 in intelligence)

https://www.sylestia.com/view/pets/?petid=1092972 (proficiencies: 5 in strength 5 intelligence)

https://www.sylestia.com/view/pets/?petid=607331 (proficiencies: 5 in intelligence 5 in strength)

How have you got your level up points distributed? Am I right in assuming that you've got them spread evenly-ish between intelligence, strength, dexterity, agility and health?

Its more useful to focus on one or two attributes rather than spreading level up points across lots of attributes. This is a helpful guide - you're best to pick between intelligence (magical damage), strength (physical damage) or agility (mitigation) - where you have three pets, it can be helpful to have one of each and maybe add a little health into each of the distributions.

Once you've got your level up points distributed, you might then want to look into equipping each pet with the most optimum equipment.