jungle exp question

so iv been haveing a small problem when starting at the start of a game being the jungler. i dont know how it should work but some times when im playing jungle and kill gromp or kruggs first it dosent give me lvl 2 right away like they normaly do. the people leasing for me did not steal the kill and i killed it and got EXP from it but it dosent give me lvl 2 until i kill both of the small monsters around blue or red buff. can any one tell me if there is something going on with the leashing that makes it so i dont get as much exp or is this just some bug i keep getting.