Hello,
Lately the JP nodes have been dropping frequently and has random spikes in ping. Is there a problem or constant maintenance?
I’m not sure that your issue is already solved or not. However at this moment I don’t know where this packet loss comes from. Did you try to specify or change a mudfish node based on FAQ - Nodes? Normaly it could related with the international cable status.
If you’re picking one locates at Japan, please pick one whose RTT stddev is closer to zero. Please check “Status -> Nodes” menu when you execute Mudfish Launcher.
No problem. 
I’d changed your data plan to PPT (Pay Per Traffic) and reset your changable date too. If you’d like to change it back I think you can do again.