Seperate title for each subplot in a for loop in Python

I am trying to use subplots within a for loop and I can plot all my graphs, but I can't give them individual x and y labels and titles. It is only the last one that it is applied to.

import numpy as np
import astropy
import matplotlib.pyplot as plt
import pandas as pd

#Import 18 filesnames with similar names
from glob import glob
filenames = glob('./*V.asc')
df = [np.genfromtxt(f) for f in filenames]

A = np.stack(df, axis=0)

#Begin subplot
nrows = 3
ncols = 6
fig, ax = plt.subplots(nrows = nrows, ncols = ncols, figsize=(30,15))

#Loop over each filename i, row j and column k
i = 0
for j in range(0, nrows):
    for k in range(0, ncols):
        ax[j,k].plot(A[i,:,0], A[i,:,1])
        plt.title(filenames[i], fontsize = '25')
        i += 1
        plt.subplots_adjust(wspace=.5, hspace=.5)

fig.show()

I can plot it in seperate plots, so 18 in total and it works fine

for i in range(0, len(A)):

    plt.figure(i)
    plt.title(filenames[i], fontsize = '30')
    plt.plot(A[i,:,0], A[i,:,1])
    plt.xlabel('Wavelength [Å]', fontsize = 20)
    plt.ylabel('Flux Density [erg/s/cm^2/Å]', fontsize = 20)
    plt.xticks(fontsize = 20)
    plt.yticks(fontsize = 20)
    

I update the title each iteration i, same as the subplot, so I don't understand why it doesn't work. Any input is appreciated!