I've experienced this for a while now, and wondered if it was worth reaching out to see if anyone else has noticed similar with the same / different plugins.
I Use Izotope's Neutron 2 a lot, and in many mixes will use it on most tracks in the project. However, the more versions of the plugin I open, the slower Mixcraft gets. It tends to be ok for audio, but the video / responsiveness gradually winds down to a halt.
I don't *keep* the instances of Neutron open - I'll never have more than one, occasionally two, on screen at once. When I restart Mixcraft, all is well - so Mixcraft is clearly not struggling to apply the processing. I would suspect a memory leak in the plugin, but my CPU usage doesn't spike. It feels like Mixcraft is still working to render the UI of hidden plugins.
Has anyone else seen the same thing - either with Neutron, or any other visually demanding / UX heavy plugins?