ICP-MS 7900 Variable Sensitivity

Is this level of variability in the 7/89/205 counts during plasma startup considered normal?

During install counts were as follows versus specification (converted to local units):

m/z Specification Result
7 > 3,000 4,896
89 > 15,000 34,144
205 > 9,000 25,086

I'm attempting to set a requirement for routine testing but an unsure what's feasible given the variability. If it's not normal, how can I go about controlling this better?

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