What do you feed?

Flowers in pots just get organic fertiliser mixed in to the compost before planting, generally at a rate of 6 grams per litre of compost. If they start to look a bit ropey during the season then they'll get some extra soluble high potassium feed once a week.

Flowers in the borders don't get anything except maybe a bit of spent compost and coffee grounds in the autumn, but that's mostly to improve the soil structure rather than directly feeding the plants. Most of the borders seem to take care of themselves and the a lot of the nutrients get recycled back in to the soil when the plants die back.

If I were growing for cut flowers I would treat the soil the same way as all of the raised beds and apply coffee/compost in autumn and organic fertiliser in spring. The instructions on organic fertiliser usually say to apply every 6 weeks but if you're also giving the soil compost and mulch then you don't need to add so many extra nutrients.

Dahlias, sweet peas and sunflowers in the ground I do give a bit of organic fertiliser when planting, but that's because the soil they are in is rubbish and as the soil quality improves (with the addition of compost and coffee grounds) I will reduce the fertilising.

I don't think you need to buy different fertilisers for each plant. The exception would be the camellias, but if your soil is already acidic then you probably don't need ericaceous specific fertiliser anyway.