If there is evidence of the leaves being eaten, and a stem that shows chew marks but is still alive, it's not damping-off. Damping off is LETHAL and you don't get symptoms AND plant survival.
Consider a physical barrier around your plants, such as a cutworm collar. Google it if you don't know what it is. Very common for veggie gardens.
Diatomaceous Earth scattered around your plants will kill bugs but DO NOT INHLAE THE DUST. Other things to try are regular insecticides, and since you are SO early in your grow you have a lot more wiggle room to play with shit like rotenone that I would not THINK of putting on a plant less than 8 weeks from harvest. Bonide rotenone with pyrethrins is a bad-ass broad spectrum insecticide. ONLY USE IN VEG!!!! I cannot stress enough.