It looks as if you've been doing the right thing from the lush planting you have. Your garden looks lovely. We use compost etc in spring or autumn on our heavy clay.

I use 6X chicken manure. It's very strong stuff so a little goes a long way.

it depends on what I am planting. I usually incorporate some fertilizer at planting time and regularly mulch around the plants in the spring and again in autumn. over feeding just wastes money as the plant will only take what it needs. it will happily feed the weeds too :o))

if you find the flowers not as large or healthy then perhaps they need a feed.