No- ants will not eat plants-it is most probably slugs or snails-have you taken any precautions?
Pesticides are fine if used correctly-there are wildlife friendly slug pellets available if you don't like the blue ones-depends on how you feel
They may not have found the other plants yet or the saliva's may have softer growth -go out after dark tonight with a torch and you will probably see a slug or snail having supper-then pick of and dispose in whatever way you choose
With any thing munched the mollusk is always the prime suspect and usually the guilty party- especially in a wet Summer
Going out after dark has greatly increased the number of slimey creatures, now residing in the big garden in the sky, for me. You'll also get to see which plants they're after.
I also use the friendly pellets in early spring.