what possible motivation could be driving you?
In the US, it's a defendant's responsibility to stay abreast of all activity in a court case. Documents filed could easily influence someone's defense strategy. Should another defendant support plaintiff's allegations against others listed, they would be expected to defend themselves w/o additional prompting.
Whoever files a document is supposed to send a copy to all parties. OK court rules though allow a judge to waive this requirement when there's a lot of defendants. In this situation, I don't see a rule that says plaintiff must absorb the costs/manpower for distributing other parties' documents.
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"We simply attempt to be fearful when others are greedy and to be greedy only when others are fearful."
-- Warren Buffett