And any ideas on how to deal with his flame buffs thats my main problem.

@Lehana,

My pets can now kill 1 fake Arth but not the real one.

@Kosa,

Hmm...not sure what more advice I could give you.

Buy lots and lots of elixirs. If you can do level 50 missions and succeed sometimes you get Strong Restore Elixir III. If you can't get those...buy Strong Healing Elixir II from the Sanctuary of Saerielle Town Hall. You'll need trusted to buy them though. If you can't get those...uh..get as many standard Healing Elixir II from the town hall. You should have friendly, so all else you should be able to get them.

Looks like you still have 2 pets with high health. I really don't recommend that. Make one a tank, the other a dps of some sort. Doesn't matter which.

For your damage pets I recommend putting all proficiency points and level up stat points into your damage ability. For your magic damage pets(that would be those with proficiencies in Light, Dark, and Fire) that would be intellect, for your physical damage ones (those would be earth, wind, and water) it would be strength.

For your tank pet (iirc your tank pet is water?), I recommend putting all proficiency points into health, the splitting the level up points between str and agi.

I agree with Lehana's statements so far.

What you want is to deal lots of damage, regardless of whether you kill the real Aryth or not (that's why you should have lots of high-healing elixirs).
The sooner you can kill ONE of them, the sooner you can get to kill another.

There's no real way to pinpoint which is which. But like what Lehana said, build the center pet to have the most HP to take lots of damage, and give the other two pets a lot of their proper stat alone so they can deal the most damage. Then when you're in the battle, aim for any one of the Aryths and try to kill it fast, and move on from there. (Don't try to take down two at the same time, it leaves them alive for longer and your pets will be barraged by 3 Aryths instead of just 2 when you take one down in less time.)

Sorry I managed to defeat them now but still I can pinpoint the strongest one using the log.