I know how things like this can be ... once we find the enemy, we wanna kill 'em all. And, if we can't? We wanna kill 'em all, all the more. But, you're absolutely right to wait ...
I'd wait even longer.
I'd get a supplement, and good quality, fresh, non-recalled, feed. And, let 'em regain full health.
And, while they do? I'd focus all that frustration and desire to kill on the intermediate host ... exchange ant for worms, as you begin to chant, "All ants must die!" As you've learned? Gettin' worms out is much easier than keepin' eggs/larva from gettin' in.
You might even come up w/ a way you could redirect your flock to another contained area, or raise them on wire during treatment, so you can later slash 'n burn (after recovering all materials, of course ~'-)