What's eating my leaves?

About three weeks into flowering on my Indica plant in an Earth Box outdoors with a sativa growing right next to it.

The Indica plant shows signs of chewage and the Sativa doesn't. Treating with Neem solution about 1x per week.

Anyone venture a guess? I am not seeing any signs of bugs or worms. My 5th grow or so and I am baffled!

it could be anything, make sure when youre treating that youre getting the underside of the leaves!

they like to hide!

once a week isn't enough if its spidermites, try every 3-4 days. they are a bitch to see & hang out on the bottom so as already suggested coat everything! good luck

ps. dont use neem when you are close to harvest. its not good the smoke. if you are still having problems then, check out SM90, its sold as a wetting agent but mites don't like the taste. after 24 hrs the active ingredients become harmless. a buddy turned me on to it a few yrs ago & I love it! I spray everything once a month till harvest I never see mites unless I forget or get lazy.
good luck ..mc

looks like something big to me. maybe a few grasshopers got in there. when they eat the leaves look like that.