The core volumes indicator gathers a lot of data. If you attach it to too many charts, it is possible that it will slow your computer down. It really depends on your internet speed and/or your computer memory size. If you find your platform slows, try having the core volumes indicator attached to fewer charts at the same time.
We have traders with powerful computers and the indicator attached to 28 charts simultaneously without issue, but it is recommended with small computer (like laptops) to have the indicator on fewer charts.