Mine are that size, same size pots but still in my conservatory, Chilly in S. Yorks. I have them in multi-purpose compost which is usually ok until I plant them in final pots in cold greenhouse. I don't usually feed until first truss has set.
Today they looked a little pale so I've fed them a VERY weak seaweed multi veg liquid feed. I only water them when the pots feel light, they're usually fine with this. Unless you have heat in greenhouse, or in a warm area, which I assume you are, I would wait until they need supporting before putting in grownbags, might need water twice a day in current pots if weather warm..maybe keep a check on colour of them as I have done.
Hope this has helped...so wish mine could go in greenhouse..I've still got herbs and other stuff in there that I daren't bring out, frost due for tonight.