If the leaf colours of your succulents babies are still as vibrant as it was when you first bought them, or even better, more vibrant now, this is a sign that your plants are growing healthily!
The appearance of translucent leaves is a sign that we should shift the plants to a more well-ventilated place. Leaves that dry very quickly show signs that the plants are lacking water.
Shape and size
Healthy succulents would also have a rather maintained shape and size, instead of becoming tall and leggy! If your plants are growing tall at a fast rate, it could mean that they aren’t getting enough sunlight. Succulents that grow too slowly aren’t healthy as well… it may be due to a poor root system or soil that is too compact. Try repotting the plants into a new batch of soil.
In conclusion, a healthy and happy succulent would have features such as vibrant and chubby leaves with layers of leaves close together :)