I treated E. coli bacteria with sodium selenite and I want to compare the selenium content at two different time points during the treatment. I repeated this experiment three times. So I have six data points that I can compare with each other.

Unfortunately, the data at the second time point is not normally distributed.

Intuitively, I would choose the Wilcoxon sign rank test in my case.

Is my approach correct?

There is obviously a difference between the two time points. But the test cannot be significant with such a small sample.

What should I do?

Thank you in advance for any constructive suggestions.