What nutrients would be suitable for growing saffron?

Saffron requires just a general purpose, complete hydroponic nutrient. For the first few weeks after the dormant bulbs are planted the flowers and first leaves use the reserves provided in the bulb for growth, so minimal nutrients are required. However, after flowering, the plant must then produce a lot of foliage for a period of eight to 10 months, which feeds the developing bulblets from which the crop is propagated and during this stage the plants need a vegetative growth hydroponic formulation or product.

I suggest you contact a hydroponic retailer and obtain a general purpose vegetative hydroponic nutrient product—this has to be a hydroponic product as many of the general purpose liquid plant foods you can buy from garden suppliers are not suitable for soilless production. The hydroponic nutrient product should contain all of the following elements: N, P, K, Ca, S, Mg, Fe, Mn, Zn, B, Cu, Mo and you will need to dilute this according to the instructions on the product (typically hydroponic nutrients come as two or three part stock solutions that are diluted with water).

Also you will need an EC meter to check the concentration of the nutrient solution—EC meters can be purchased from your local hydroponic retail shop. Saffron should start off at a low EC of around EC 1.0, increasing to EC 2.2 when foliage has grown. Also, it need reasonably high quality water (rainwater should be fine, but avoid city water supplies due to the water treatment chemicals they contain).