For instance, if your garden goes through a dry spell, all the peppers will fight to get as much water as needed, which may stunt the growth of the plants that couldn't compete.
In another scenario, taller peppers could cast too much shade over smaller plants and inhibit their growth. So, it's better to spread out your peppers throughout the garden.
Jalapeños and other peppers planted together may also increase the risk of spread of diseases, which may be transmitted from plant to plant if foliage or fruit touch each other.
the soil, peppers planted together will collectively suffer. For instance, overwatering affects every plant in the area, and saving them all will be hard.