Could be, or possibly grasshoppers which I had problems with until I sprayed my outdoor with insecticide .
I've got a bagseed grow going as well. What I did was got the bottle of Bayer Advanced insect killer (the blue bottle that attaches to a garden hose) and sprayed my plant as well as my other trees shrubs and especially the entire lawn. This worked very well.
I had the same exact experience and all I did was look on the stem and beneath the leaves and found like 4 caterpillars so I just picked them off and no more leaves were eaten but my plant is still recovering...
trust me .....i searched every inch of my plant when i saw that... even looked at the affected area with a 60x and 100x louper