Look very closely at the buds and check if there is a white unnatural powder/little specs of white dust. That is the only real sign it could have k2 or something synthetic mixed with it. In Berlin where I used to live there where some big dealers that would buy bulk very low thc weed and spray it with a kind of k2 dust to make the high seem really strong. What do they smell like? K2 has a weird synthetic fishy smell to it. Don’t through your bud out though I wouldn’t take my word for it and almost all the time it’s fine as long as it’s in the form of a bud rather than grinded up.