What medium are they rooted in? I am assuming rockwool or hydroton b/c you have them in ebb and flow. What kind of nutes are you using? When then have roots, put them in a bigger cube or some more hydroton and start feeding them 1-1-1. 1/4 strength nutes is too low for rooted clones. If you want to be really careful, try .75-.75-.75. Peace.