There may be several factors involved, and with presently available information, it is unclear to me what is happening.
Looking at your screen shot of 4 browser instances, perhaps consider:
1. If all 4 instances of Expert Advisor Studio are configured identically (same pair/instrument, same Data Horizon, same EAS configuration, I would think that Task Manager should show 4 CPU's having similar and higher utilizations than any CPU's beyond 4. But, yours doesn't. Perhaps one or more EAS configurations are different?
2. I am concerned that Task Manager CPU information does not look as perhaps it should. Your CPU, an Intel Xeon E5-2630 v4 has 10 physical cores and with Hyper Threading, is capable of 20 threads, but yours is showing "virtual processors 10" instead of what I would expect should be "cores 10, logical processors 20", plus a few other differences (for comparison, see my attached screen shot for a computer with dual Xeons). My first guess is that you have a configuration problem somewhere, which might be affecting one or more things.
3. I wonder: is your computer BIOS configured to enable Intel HyperThreading, perhaps labeled "virtualization"?
4. If so, I next wonder if your Windows 10 is configured to boot normally? Perhaps examine your settings showing in the msconfig utility, especially Boot tab, Advanced options button, and make sure Number of Processors option is not being used to reduce CPU core/thread availability.
For comparison, my attached screen shot is showing CPU Utilization (using Windows 10 Pro 1903), per your example, running 4 instances of EAS (using the Opera browser, which I think, should be very similar to Chrome), with 4 of the CPU's showing higher utilization than the others, as expected. Beyond that, mine shows information which yours does not: number of cores, logical processors, virtualization enabled, and amounts of L1 cache, L2 cache, and L3 cache (while yours shows N/A for all cache information).