Well since you cannot be sure how old the bulbs are then for sure go and replace them. Pick some good quality bulbs from a dedicated Saltwater store.

Avoid the generic common bulbs from the bix box retailers.

Mind you I don't have any T5 experience, just MH. So take this with a grain of salt...

How often do you change your lights?

One of my friends has 8 T5 lights. All different colours. He has sps, clams, duncans, acans, leathers, etc. All doing great. Been 3 yrs. He changes the lights every 10-14 months.