Deconvolution and image brightness

So this is the original image:

Adding noise to the image:

noise_variance = 0.05;
noise_blur_img = imnoise(blurred_test_img1,"gaussian",0,noise_variance);

and this is the restored image using deconvwnr:

imden = wdenoise2(noise_blur_img, 9);
signal_variance = var(dimg_test1(:));
NSR1 =  (noise_variance)/(signal_variance);
img_restored2 = deconvwnr(imden, PSF,NSR1); %PSF = fspecial('motion', 21, 5);

My question is: why is the restored image using deconvolution made the image's brightness go down ? And how can I fix it ?

P.S: I am still getting used to posting quetions on Matlab so I apologize if the formatting is wrong.

EDIT: I have attached the original image and the code with which I added noise and blur.

[KALYAN ACHARJYA]

Hey, the question you asked is quite clear. The question is not directly related to MATLAB, it is a subjective question. It would be better to answer whether can you attach images? In fact, I would like to see the noise distribution in a noisy image.

[Kajimusugura Hoshino]

Hello,

Thank you for the quick response! I have edited my question posting and attached the orignal picture on which I performed blurring and noise addition.

Thank you so much once again. Please let me know if there is more information I could be providing.

[Pratyush Roy]

It will be extremely helpful, if you can provide the full code so that I can reproduce every step from my end.