is this cat flu?

I got one of my cats when she is already one year old.  she is a spayed white Persian girl.   The previous owner told me that she has been vaccinated. however, now I have some doubts about it. All of my other cats had been vaccinated except this one. and they are all indoor cats

she is healthy normally, however, I notice sometimes she had sign of cat flu. eg. she might start to sneeze a lot , for a few days, then back to normal.

sometimes , she will squint her left eyes for a few days, then back to normal again. 

to me this looks like mild sign of cat flu.   if she does have it, can I still vaccinate her?  or she already has antibiotic inside her already, as she been exposed to the virus?

another reason I am worried about is, recently my other cat gave birth to 3 kittens.   although kittens are very healthy and active, I did notice something , such as kitten squeeze now and then, they have a little bit black gunk under their eyes, not a lot, just a little bit.  also one of kitten has teary eyes.   

none of these are obvious, but there are mild signs,  does that mean the kittens are already infected by this white girl? if yes,, can I still vaccinate the kittens?

btw, none of my other adults cats have these signs.

many thanks

Bump

Sounds more like allergies since it comes and goes.  I would talk to the vet about both your new kitty and the kittens and find out what's going on.

Thanks for bumping :-)

I read somewhere, once infected cat flu, some cat become carrier, they do not show signs , unless they are stressed. In this case, she has it sometimes, then back to normal, does not it sounds like she is a carrier? many thanks