On my 10 year Star Ruby Grapefruit, I've noticed in the last year so branches dying back, seemingly haphazardly out of the tree. Is this a normal thing, or is it the sign of some citrus disease? I'll some pictures though I've already cut out some bigger branches that died, but I'll try to show what a smaller dying one looks like....

Oops, found some gummy looking residue on some branches.....would this be Gummosis? The stuff is no longer gummy, but hardened....how to treat?

THANKS...MangoDog