Hey,
So glue on large caps is normal. You can’t tell it’s glue cause it’s pretty solid or rubbery. Even if it’s started to get flakey and brittle, it’s fine unless you are taking your gear on the road.
If it is viscous it’s probably the electrolyte and the cap needs proper removal, the board needs to be cleaned and new caps replaced.
If it's brown and around solder pads it's probably flux which wasn't cleaned off well enough after assembly.
Also, any bulging on a cap is a clear sign it needs to be removed.
Best,
Erik