healthy adult cat with goopy eyes, sneezing

Question
my healthy 12 yr old female cat starting sneezing last night (just a little) and has a bit of goop in her eyes that hardens her eyes shut after her nap. she seems fine but I need to leave town for a few days on Tuesday. Is it just a cold or signs of something worse. We are a four cat household all healthy mostly indoor cats. All were regularly checked from young age with all shots/tests etc.
Just started last night.

Answer
Well you said you have a houseful of healthy cats. This cat is 12 yrs old and this came out of the blue. I am guessing she is an indoor cat.

That would indicate that something is going on and if this were my 12 yr old cat I would have her at vets first thing Monday morning.

She has apparently picked up an Upper respiratory virus. This can be mild or can get out of control quickly due to her age. These are often contagious as well to the other cats.

Your safest bet is to have her looked at Monday at the very least. Then you can leave knowing what's going on with her.