tips of leaves are being bitten

At my buddies veg set up one of the plants there is apparently being bitten by some insect because i can see tiny little bite marks. The bite marks are coming from the outside inwards and look very distinct. The entire main tip of the new set of leaves has been bitten off and i want to stop it before it gets the other plants. needless to say there is no bug when anytime i look. Can anyone help me out? i have some spray that i got from canadian tire that seems to be working on my out door plants or atleast not harming them for that matter. Will this work on indoors aswell? i dont want to go to harsh chemicals so quickly but i have seen no results anytime i've used neem oil, and i plan to flower soon within a week so i want to get rid of the problem asap. thx

Pictures would be a help. It is pretty hard to help out unless I have a visual.

Without seeing pictures 4 sure, its hard 2 say, but sounds like Vine Weevil.
Read more about them n removing them here:
https://www.rollitup.org/bugs/223611-guide-recognising-removing-bugs.html

Hope This Helps - XxNinjaxX