These particles are only its decay products. These gluons are exchanged very often, so the quarks feel each of other. Neutrons do not always decay. Let me be more specific. You know, that most of the matter around us is made out of atoms.
Atoms have nucleae and electrons.
In the nucleus you usually find protons and neutrons. In other words, when a neutron is hidden in an atomic nucleus, it is extremely stable and it does not decay according what you wrote. On the other hand, if you have a free neutron, taken away from a nucleus, it does decay. When a neutron is buried into a nucleus, it feels mostly the strong interaction. For the neutron decay, the weak interaction is responsible.