Teemo e and cassiopeia poison and singedpoison

So teemo's e passive is dealing dot dmg every second and its listed as a pisonwhy doesnt it proc liandrys and rylais. Why can cassiopeia's poison proc both rylais and liandris and why does it happen the same with singed's q ... Not my problem till now listed to this... If a target is poisoned by teemo or singed cassiopeia's e will go off cooldown to 0,5s .. Why doest then proc the fcking liandris and rylais ... I am not saying rylais and liandrys shou proc the on hit teemo's e but the pioson should be ...