So-called soil fatigue is when you dig up a plant that has been there for many years and put the same plant back in exactly that spot. Even if it's a young plant that you can expect to grow quickly and bloom profusely, that's not going to happen.
Roundworms could be to blame
It has not yet been possible to clarify exactly what is responsible for this. It is assumed that nematodes, for example, are responsible for this. These are nematodes that live in the soil and can damage roots, stems or even leaves. They are also called rootlets.
Changing the location of the plants
Perhaps one day we will find out whether this is actually the cause. So if your plants don't want to grow as you imagine, then look for a new location for them. Alternatively, you can replace the soil at a depth of one meter. Not all plants behave this way. Particularly susceptible are roses, raspberries, apple trees and cherry trees.