11 day old seedling growing slow but looking healthy, help!

This is my first grow. I have great white shark growing under two 24 t5s. No nutes yet. Just phd water. My seedlings grew crazy for the first few days of sprouting. But I've noticed that it has hardly grown for the last 6 days if it has at all. It's in my dwc now. Any ideas if anything is wrong?

Rw cube is too wet.. It cant grow because its not getting any O2.

I would agree with that, let your cubes dry out slightly every couple of days, will do a world of good