Your pics are a bit out of focus but it doesn't look like a problem.
The last place I would expect to see any mould or fungus would be the stem of a mature plant.

It just looks from here like the way stems usually go to me but if you can get a clearer pic it would help.
brainfood33 Reviewed by brainfood33 on . Help Urgent Hello i am growing 3 northern lights plants in dwc and all was going well until yesterday that i saw that the stem of 2 my plants is getting weird i suspect a fungus i will post some pictures any help will be greatly appreciated thanks in advance Rating: 5