ggplot with aes_string and mean()

Question

I have the following function:

histograms <- lapply(names(stock_markets[2:ncol(stock_markets)]),
       function(n){
         
ggplot(data = stock_markets, aes_string(x = n)) +
  geom_histogram(aes(y =..density..), color = "darkblue", fill = "lightblue") +
  stat_function(
    fun = dnorm,
    args = with(stock_markets, c(mean = mean(stock_markets$`n`), sd = sd(stock_markets$`n`)))) +
  scale_x_continuous(n) +
  ggtitle(paste("Histogram of", n, "with Normal Curve")) +
  xlab(names(n) +
  theme(axis.title.y = element_blank(),
        axis.line.y = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank()) +
  theme(plot.title = element_text(hjust = 0.5))
  
})

which basically plots the histograms from the dataframe stock_markets. Each column contains a stock price. My issue is that I used aes_string to get the names of the columns so that I could use them in aes but I can't figure out how to use the mean() and sd() functions with the n argument (which is the column I need) so that I can superimpose the normal distribution on the histogram.

I have tried:

mean(n) mean(stock_markets[n]) mean(stock_markets$`n`) mean(stock_markets$"n")

but nothing seems to work.

Any help would be greatly appreciated.