Rooted clones need nutrients and light. As soon as I see roots coming out, I feed mine 1/4 to 1/2 strength nutes and put them under 300w of T5 and cfl lighting, they grow pretty quick from there!
To keep your clones healthy, just keep them under mid stength light (2 bulb T5 is sweet) and give them nutes every few days and water in between. Give them some B1 vitamins and nitrogen as the nutes and they'll survive well.