small brown spot on a single lower branch

[gro]

there is a small brown spot a single lower branch on one of my pandoras in 3gal promix under 1000watt hps in a 4x4 tent temps are around 75-80 lights on and about 65 lights out. they are 45 days old and get water about every 4 days when needed, they have had deficiencies from under feeding previously but that has been corrected but the old leaves are still there but this is unrelated to the current concern. I harvest in 30days, now I am worried about some sort of stem canker but it does not look like any pictures as it is only one spot on a branch and it is not at a node and not spreading. I am hoping this is nothing, and i am just being cautious, I always panic and almost kill plants, i have to stop doing that! i have a picture but i cant figurre out how to add to galary

 

[gro]

i hope i am just worried about nothing.

 

[gro]

looked some more and I am going to try to forget that I saw it. It is a tiny looking wound spot. I thought it was just dirt, which describes the size and color.