Rocket is fine to give, providing it's washed etc;
Tomato is a no no. I wouldn't feed it to any dragon.
Grapes are a treat only.
Best staples are butternut squash, cress and spring greens. Spring greens can be purchased in Sainsburys for 99p for a big bag. Cress can also be found in Sainsburys for 25p per pot.
Dragons can't see still water so well. Best way to keep them hydrated is to soak/bath them. They absorb water through theyre vent.
An indication to your dragons hydration is in his/her toilet