Another nooby question here, sorry haha
Not sure if I'm doing something wrong, but I recently finally expanded my party limit to 2 pets, and have made it all the way to Umbra Forest (both now level 22) but for some reason only the 2nd pet will attack (I click on the enemy, use an attack, end turn is green and they take damage) but when it comes to the 1st pet, if I click on their attack, it skips them, no damage is done, and is back to the 2nd pet. What is going on?

It's not suposed to happen, tho i saw that you have a water pet so it may be the explanation. Water pets have a finisher called ice barrier, if you select it you does not deal damages to the oponant, instead, the move will absorb some of the damage receaved and heal your pet.