To really know what the mixture of any fertilizer should be for a given soil, a soil test should be conducted. Home kits are available and give, generally, fair results.
In lieu of that, tomatos need slightly differing fertilizers for differing growth stages. Suspecting your plants are fairly mature, look for a mixture that's higher in phosporus and potassium than nitrogen. The bag or can will have the mix on the front looking something like "9-7-3" or some such. The first number is nitrogen and should only be used sparingly... the phosphorous (second number) is important for root development and potassium (last number) is more important for fruit devleopment. I'd look for something like 4-6-9 or reasonably close...
Keep in mind, if you could use a good compost you wouldn't have to fertilize...
Plenty of water right now... keeping soil damp but not standing water. Probably at least 1 inch per week. I like to keep the base of the plant covered in peat moss to assure the roots are cool and damp...