I agree,sounds like too much water ,have had the same problem with rockwool before, or they are stetching from not having enough lumens like zandor says.Seedlings use very little water, because they have a very small root system.Rockwool can become saturated with water quick, especialy after it has been squeezed,like so many people often do after presoak.I would say back of the h2o a little ,and move the hailde to 2.5 foot from the tops ,then lower the light 1" at a time(several hours or a day) from there until the plants start growing out instead of up.
just my opinion , I could be wrong