louieRD-
It's a common and ongoing problem with that machine design.  Those are your return lines to the fuel tank.  Whatever the machine does not consume from the injector pump goes back to supply, they are low pressure [really low] and wont effect the way the Continental runs or allow air into the cylinders, but they will make one hell of a mess real quick.  On my Classic III D of similar vintage, my return lines are braided hoses that squeeze onto a little "tit" right next to the injectors.  The hose simply wear out and gets loose, degrades and then fuel starts leaking.  You can try pulling them free [very easy to do by hand, just give them a twist and a pull] and trimming them back 1/8" or so.  You might have enough good hose at that point to get a decent seal fit but maybe not.  Best thing to do is get to a diesel repait shop or welding repair shop and get a length of new hose and replace them all.  The hose is cheap and if yours are leaking it probably time to replace them.  Buy enough to carry spare hose.  The new stuff will degrade as well and then you have another mess.  Just match the lengths of the old hose or give yourself a little extra for another trim the next time and you should be good to go.  The last cylinder [to the right on my machine, facing the injectors] is just a short tail of hose that doesn't return but has the "tit" on the injector.  That one you just plug up.  Most guys just use a slightly oversized machine bolt that will plug the line.  A mechanic might offer a better plug, ask them.  Lasr thing- getting the return line braided hoses back on tthe little "tit" next to the injector can be a pain.  There is no hose clamp they just fit seal snug, so you MUST replace the hoses with the correct size hose.  They come in a few incrementally small diameters which need to be replaced with the same size or it will leak.  If you pull one of your old ones any diesel shop should be able to get you fixed right.  It's not the best design, but I love the Classic III D capacity and the Continental is a workhorse.  This is just a maintenance issue you live with.  BTW- take care removing the old ones and check that "tit" for any leftover rubber stuck to it and make sure no little particles of the old hose  get into that little "tit" or the injector.  Ask me how I know.

Like YoJimbo said, go to a deisel repair shop. Those small hoses are almost impossible to find anyplace else.

Ask your nearest Deutz dealer for part number 1398326, i believe this hose is the same size and has the nice outer covering as the originals did.  If its one particular hose popping off each time you may have an injector return port clogged already.