Python: I want to check if row has multiple same values for any of the columns in a dataframe and if yes, replace the repeated value with null

Question

I am new to stackoverflow, please excuse my formatting

My DataFrame looks like this:

Col1    Col2    Col3    Col4    Col5

A       B       null    A       D
A       B       C       F       C

Since in the first row, Col4 has a repeated value i.e. A, I want to replace it with null.
Similarly, in the second row, Col5 has a repeated value, I want to replace it with null.

The final dataframe should look like:

Col1    Col2    Col3    Col4    Col5

A       B       null    null    D
A       B       C       F       null