Fusarium/Verticillium wilt??

I am an indoor grower in grow tents. I run coco as my medium and the plant I am referring to is about 1 years old and is a mother plant in a 5.5 in square pot. One of my veg plants started wilting on one of its branches. First I thought it might be root aphids but using a microscope on my phone I saw no sign of the buggers. Then I thought possibly one of the wilts. So I took the plant out and chopped it down at the base. There is definitely discoloration in the xylem of the stem. Other than the one branch wilting and also the lack of uptake of water(pot was drying out maybe 3x slower) there was no other symptoms. This is the second plant this has happened in about a month and a half. First time I thought the same but when I cut the trunk there was no discoloration.
I have attached pictures of the plants base stem cut. Any help with diagnosing would be much appreciated.

Another side note. You can see that I peeled some of the outer layer off and also cut the base in half to look inside. I tried to squeeze it together as best as possible

Here are some pictures of the roots. Slight discoloration from nutrients. I run megacrop right now. I used to run maxibloom.

The rest of the nutrient line up consist of:
Protekt
Calimagic
SM 90

Two more pics of the base split in half. Can see the black streak going up the center.

definitely some kind of rot. I would try not to keep a plant in the same pot for a year. Transplant or follow bonsai mother techniques where you cut back the root mass every now and then. Were you watering that multiple times a day? This has happened to me with things that I kept in the same pot for a long time and they were severely rootbound. I don't know the exact cause though

You've done a very good job keeping those plants growing so long in coco. It looks like your plants have exhausted their space in the containers. I hope you are keep cuttings off of these plants in newer soil. A fungus like Fusarium/Verticillium wilt will kill the plant and cuttings. I think your problem is from being in the same container too long. If you have live cuttings off the mothers then its not fungus.

if you want to keep mother plants like that,
for an extended period of time....
i would advise you to keep em in organic/living soil.

coco is a very unforgiving medium.

you can grow all your clones and flowering plants in coco.

but keep your mothers in soil.

imo, they can only go so long without all the micro/macros and bene’s which are found in soil and keep them healthy.