Context:
In ROTN 3.2.1 (Perhaps other versions as well) on a multiplayer server.

Player 1 wears an obsidian helmet without the helmet hidden.

Player 2 looking in the direction Player 1 (i.e. causing the helmet to render) will dramatically increase memory usage every second, this can be tracked with Task Manager.

As soon as player 2 looks away from player 1 the memory leak stops.

While player 2 is looking at player 1:
As soon as player 1 takes off the helmet or hides it (Still equipped) the memory leak stops.

This is with the prism launcher, no extra mods added.

It is not easy to debug a full modpack; if this problem occurs even after disabling Aqua Acrobatics, it would be useful to narrow down what mods are necessary to reproduce this in isolation.

pretty sure this is about 3d armor implementation, not aqua-acrobatics
i reported similar issue long time ago for roots mod, was been fixed back then
MysticMods/Roots#154