Probiotics are to colonize the gut with good bacteria. Electrolytes are to keep their body fluids in correct chemical balance. How old are the chicks? They shouldn't need electrolytes more than a day or two. Chicks should be able to choose between drinking electrolytes, which have a fair amount of salt, and plain water. Imagine if you were very thirsty on a hot day, and all you had to drink was salt water. Sometimes, on a hot day, you need that bit of extra salt, to keep your body balanced. If you need it, and don't get it, you will feel very sick. But... if you don't need it, plain water will meet your needs, and do it better.
Once the chicks guts are colonized, they don't need the probiotics. One thing you can do to help them is to give them some soil from your yard. I give them a plug of sod, with the grass attached. Simply place it upside down in the brooder. The chicks get: beneficial bacteria and fungi, minerals, first grit, first greens, a few insects and seeds, first dust bath, and infinite play opportunities. they also get first exposure to the pathogens in your soil, including cocci. This is a good thing. They need this exposure to develop a healthy immunity. cocci are a natural flora in a chicken's gut. It's only when they overwhelm the good guys that the chicken gets sick. By exposing them while they are still in the brooder, and during the first 2 weeks, while their natural immunity is at it's highest, you are helping them to have a strong immune system for life.
