Hi, can anyone recommend good sources / brands of plant food that I can
buy online (there are no decent shops where I live and I don't drive).

I have
10 x Cacti
2 x succulents
1 x fatsia
1 x Kucle (citrus) plant.
Lots of outdoor plants on my balcony.

Everything is in pots, I don't have a garden.

Sorry if this sounds dumb, I'm new to this! :-)

Cheers,

Tom