Inspected Seedling root. Has some discolouration. Can anyone recognise if this is root rot or not?

Hey guys, this is my first grow. I'm kind of just experimenting right now, and I know my conditions / set up aren't great. I could have taken more care / designed a better system. However, I was super happy when my seeds germinated and my journey with my first girl has begun.

I'm a little concerned. She germinated a few days ago, and the root looked like a healthy white! Now, though... she has started taking on a slightly brownish colour. I've attached an image for better inspection (note, if you zoom in on the photo you can see it more clearly).

Anyone got any clue if it is root rot? I would totally understand why if it was. Thanks so much for your help!