Yes, in broad terms you can re-(silver) solder.
No special tips, just the usual, degrease, and clean scrupulously, flux and heat area thoroughly, etc. etc.
Let the added silver-solder flow into that already there to make a single liquid ‘seam’ at the point of leaking and make sure the newly added silver solder runs into the joint.
It is however worth considering why the original solder job failed to take at that point and making sure that whatever that fault was you now have it covered……