From this journal (mankand1988), I found that Monod model for multiple nutrient is as follows: (for three nutrients)
μ = (μmax /( ∑ (Ki/Si)))* (K1/(K1+S1)) * (K2/(K2+S2))*(K3/(K3+S3))
For my case, all three nutrients has different K, S and μmax. So, here what will be the value of μmax , is it the maximum or minimum or average of the three μmax values?