Your succulents need fertilizing just like all of your other plants, but in a lower dose. Plant fertilizer is needed for your cactus & succulents to promote good growth and to stay healthy. The nutrition ratio for fertilizers made for cactus / succulents can vary between different producers, here is one example:
1,4% Nitrogen (N)
0,7% Phosphorus (P)
2,7% Potassium (K)
The rest of the fertilizer consists of other macro- and micronutrients, like Calcium, Magnesium and sulfur.
Nitrogen (N) - promotes good growth Phosphorus (P) - promotes budding and rich flowering and Potassium (K) - helps the plant build strong stems and a strong root system