Hi Paul, There is no *need* to do anything else. I think your system is a great one. I, too, find my organic tomatoes smaller, but so what, I get plenty of them. I also really believe in a thick organic mulch. It helps in so many ways and contributes nutrients as it decomposes.
Lots of organic gardeners use blood meal for nitrogen and bone meal for phosphorus and all sorts of other things like kelp products, cottonseed meal, etc. The way I look at it is that gets pretty expensive and I'd rather not spend so much. One of the reasons I am growing my own is to save money. I don't see a great harm in throwing some synthetic slow release fertilizer on the plants or crops. This would not be organic, but I don't see it as really bad. I have stopped using that for a while now, because really when you consider the manufacture, packaging, and marketing of those products, it's not so good for the environment. So I do the mulch/composting and I find things work well. I have lots of birds and bees, and spiders. I don't have real bug problems, it seems to be pretty well balanced, and I feel better about what I'm doing. Happy Gardening!
Laurie

Compost does not have the soluble, readily available, nutrients that "fertilziers" may have and that is why compost is not sold as a "fertilzier", but that does not mean those nutrients are not there, they just are not very readily available, not seen in a test that checks for readily available nutrients.
The only way to know whether you need to spend money on supplemental nutrients is with a good, reliable soil test, adding any of those with that to guide you could result in a soil that is unbalanced that can create conditions that will attract insect pests and plant diseases.
After some 35 years of compost, and other organic matter, my soil tests indicate the soils pH is 7.2 (a bit high) with optimal levels of P, K, Ca, Mg and nothing other than the compost has been added since the first test showed the soils pH was 5.7 and there was a lack of P, K, Ca, and Mg.