Toxic Spikes vs Toxic - poison damage not functioning properly

[Zinsmiter]

I was fighting an Umbreon and it entered under my 2 layers of toxic spikes. It got poisoned as expected and the damage was scaling up.

Then suddenly after the 3rd or 4th turn, the damage got reset as if it wasn't poisoned and i just made toxic. It used Toxic on my Starmie itself

so there may be some complication with opponent's Toxic resetting its own or something? I don't know but i thought the information could be useful.