Zyra passive seed not spawning in 3v3 in tower area

Zyra passive don't spawn seed undertower when they are up(should be normal) But after destruct the first and the second tower at bot lane the seed are not spawning in the tower area(only spawning in the bush and entry jungle otherwise the passive is still available and spawn when it can in normal area) but after destructing the third tower everything goes back to normal and seed spawn normally.