Hi Kali,
I'm loving your "The Elementals" series.
Thank you for making the effort to return to the story after all the changes in your life, and congratulations on getting married - or maybe I should be congratulating you partner on landing such a great catch!
I'm hoping you'll be able to get more chapters written soon. Part of me wants to say "Get on with it!", however I'm getting the story for free so that would be a bit much!
I don't know how much you've fleshed out the next chapters, however it seems to me that now that the enemy obviously knows about the island there needs to be more focus on warning systems and defensive training and preparations. I have some ideas (below), however they would probably mean that you'd really have to improve the enemy's attack to make for a dramatic battle.
1. Earth Elementals to create a network of tunnels so that United Elemental Alliance (UAE) personnel can safely get within range of the enemy.
2. Fixed video and drones to supplement Earth Elementals earth senses so that they can attack from below, sinking the enemy into the ground.
3. Radar for early warning of attack by air or sea. Possibly sonar/passive sonar in case of submarine attack.
4. All Elementals to practice air defence, including against artillery and missiles, and including different skills working together - e.g. Earth Elementals providing ammunition for air and storm Elementals to throw in the path of missiles, etc.
5. Air, storm and water elementals to practice working together against sea vessels.
6. Specialist elementals, e.g. Stella and Jake to practice using their skills. Jake's the ideal person for stealthy reconnaissance etc.
Regardless of what tactics you decide to have the UAE use, it would be fun "watching" them training as part of your story, particularly as you'd throw in a few twists.