I bought these cacti from Next in a pack of three for £1, so I thought they were fake, but they started growing after a few weeks. The picture shows them as they are now, but I've no clue what I am doing. I water them weekly, and they live in the kitchen window, but that's all I know.
Please, can anyone tell me, do they look okay? Do I need to do anything with them? The soil is running low; any idea what I should buy?