Insects after introducing fertilisers.

Fertilizer and the appearance of insects is pure co-incidence, there is nothing in fertilizers that makes insects think about eating your plants. Cannabis does not produce terpenes to attract pollinators, cannabis pollination is wind borne and completely random.

Difficult to stop outside, plant creates terpenes with the purpose of attracting pollination. Plan ahead, have tastier, prettier, smellier plants as Companions, insects will go for them first leaving yours alone.

Bugs often hide or lay eggs in compost, so it's important to get it from a reliable place. Photos of the bugs or damage will help a lot with how to handle them.

any photos of the pest? what was this special od fertilizer? seems weird they only coming after the fertilizer was applied. Maybe its the fertilizer they are after and not the plants. they look ok in the pic. You could put a mesh aorund them or something or u could bring them indoors or treat other bait plants like herbs or something with the pesticide and hopes they go for it vs your weed. bait crops are nothing new but a good solution to a lot of problems with pests.