svchost is a program used by Windows to host inbuilt Windows services (which could be running a desktop theme, Windows Defender or font support). It's quite normal to have 10 instances of svchost using a fair bit of memory in total. It is possible for malware to disguise itself as an svchost.exe instance, but like you said, it's probably not malware if the problem is persisting across formats.
This program might give you a little more info than taskmgr as to where your memory is going. Try it - it even shows you which services are being hosted by each svchost instance.