All channels in an agent get slower after a channel is full

Hi,

In my cluster, I have an agent with one source connected to multiple
channels. Each channel connected to different sink (1 channel paired with 1
sink) which send events to different agents (like one to many relation).
Just like the multiplexing flow example in Flume user guide website.

However, when a channel reaches its capacity (already full) I see that the
agent performance gets slower.

What I mean by getting slower is that, all other channel-sink pairs in that
agent also get slower when sending events to their destination. I can
understand if the overfilled channel-sink pair get slower, but why it
affects another channel-sink pairs in that agent? From what I see here, the
other pairs should be independent with the overfilled channel except that
they use the same source, right?

Thanks!

Regards,
Vincentius Martin