why does the replication latency keep growing?

I have a transaction replication. From replication monitor,I see the latency keep growing up to 2.08:14:13.I alread introduce the parameter-SubscriptionStreams 32,-–MaxCmdsInTran 5000,-CommitBatchSize 5000 to improve formace. But the latency still keep growing.Compared with this subscriber,another subsriber has a good performance in terms of seconds latency.

How can I find the bottleneck for the bad performance?

What measure I can perfome to reduce the latency.

Thanks