Rat food?

Would it be okay to feed my rats a mixed store bought food? I'll also feed them oxbow food.

I would only use that as a treat.

But there younger so I thought they'd need extra stuff

Could I give them oxbow and the mix and keep it in the cage 24/7 and feed them extra stuff at night like veggies

I wouldn't give them the opportunity to choose things out of the mix. I would let them have free access to the oxbow and maybe just a couple hours a day have the mix available.

Mix is a bad idea .... they pick and choose so do not get good nutrition, there are unhealthy things in mixes, there are things in mixes that rats can not digest, and sometimes mixes contain things like dried corn which can contain mold
(plus corn is very unsafe unless organic/nonGMO)

A good quality block like oxbow regal rat available 24/7
daily vegs
and healthy treats like a piece of fruit, berries, melon, a piece of organic cereal, cooked grains etc

If you want to supplement (and you don't need to) then organic soy infant formula thickened with a bit of baby cereal (kind that says add milk) is ok

At least 2 or 3 sources of water in the cage are very important and at least one source should be a water dish that can not be tipped - young rats often look like they are getting water out of water bottles but their tongues are not strong enough to move the ball bearing so they can't actually get any water.

Thank you that helped so much I've just heard people giving their rats a homemade mix 24/7 plus lab blocks and wondered since mine are young if I should to.

I would stay away from store bought mixes. Even though it feels like they should be good for rats (since that's who they claim to be making them for) it's usually pretty bad. You could opt to supplement with some healthy grains occasionally but I have been given free mixes and would still never give them to my rats.