wordpress seems to be using over a gb of ram

Hey Everyone!,

One of my wordpress websites is suddenly using a huge amount of ram,

in the order of 1gb + virtual ram.

ive tried disabling the plugins and switching the theme over.

when i switch them all back on one at a time nothing goes wrong it takes time before the problem flares up.

theres been no signifigant changes recently,

i am on a good host, and the sister site of this one is in a different account but same host and doesnt have a problem.

I am wondering what tools or procedures other people use to narrow down problems like these,

any help would be appreciated,