Why do I keep getting videos darker than the frames from which they were made regardless of the software I use?

Question

I have tried using both VSDC and VideoPad for editing videos, and both of them randomly darken the videos I put into them. Is this a common issue? If not, what information do you need me to give to solve this problem?

This is a problem I have had on multiple computers now.

Here are some side-by-side comparisons, with each pair being first the input video and then second the output video.

You can see that this second image is darker.

You can see that this second image is darker also.

Edit: I tried editing the video with FFmpeg, and it did the same thing.

Edit 2: Here are the outputs of ffmpeg -i [videofile]:

Original video:

Metadata:
    encoder         : Lavf58.12.100
Duration: 00:01:32.75, start: 0.000000, bitrate: 1012233 kb/s
    Stream #0:0: Video: huffyuv (HFYU / 0x55594648), bgr0, 1920x1080, 1012406 kb/s, 60 fps, 60 tbr, 60 tbn, 60 tbc

Edited video:

Duration: 00:01:36.98, start: 0.000000, bitrate: 514031 kb/s
    Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 1920x1080, 512695 kb/s, 59.99 fps, 59.99 tbr, 59.99 tbn, 59.99 tbc
    Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s

Edit 3: The original video was compiled from a series of .png files. Here is the command I used to do so:

ffmpeg -framerate 60 -i %05d.png -c:v huffyuv -pix_fmt rgb24 output.avi