To be honest this is the first time i've seen this issue on MJ !
Original i thought it may of been a mealy bug issue also known as scale bug & are a bit of a sap sucking pest which may leave simaler symptoms ! but with out presence of bugs a bit hard to say & even harder when its an indoor grow...
We also have to look at other plant issues which may cause symptoms like these...
Sush as...
Guttation
Guttation is another clear sign of your plant's trouble. This condition causes the plant to secrete, or drip, sap from the margins of its foliage. Guttation results from the plant's roots taking in more water than it is able to process. The buildup of unused water develops a pressure within the root system. The plant releases the pressure by secreting the sap through its leaves.
I'm not totally sure if this applicable to stems tho, but worth noting.
Well as Fuzzy said, Its something I havent seen on weed before - on the stems anyway. My last grow, I fed my plant GOLDEN SYRUP diluted in water, NOT RECOMMENDED!! And she started showing weird symptoms on her leaves, I couldnt fix the prob, I tried every remedy and I only barely saved her. When I harvested, I noticed that some big fan leaves that were having trouble had actually started to excrete small globules of the G/Syrup I think it was. Thru the veins of the leaf they were getting blocked off from the syrup and showing defic. symptoms etc; it wasnt until I noticed a few of these secretions under a few leaves that I thought it may be the syrup - being ever inquisitive, I decided to taste the stuff, and it was a very similar taste to the syrup! So I was choking my girl.. But yeah, other than this thats the only time Ive seen it.
AND THANKS FUZZ FOR THE GUTTATION INFORMATION Goodluk, Smokemup