I'm new to growing in bubblers, i've got a white widow in a bucket now and it's roots are growing crazy. Just curious to where your water level is in the bucket. From my experience and what i've read when you put your rooted cutting in the hydroton you should plant it so the roots are close to the bottom of the pot (maybe 1cm of pebbles then the bottom of your rooted stem) then have the level of water in your bucket so that it just touches the bottom of the net pot, lower the level of the water as the roots grow into the res so that you have a gap between the net pot and the water 2-4" so that a good portion of the roots has access to oxygen.

It sounds like your res temp might be a little high too, ideally it should be 65-70F, i wouldn't of thought it would slow root growth as much as yours sound like they have but they won't grow at full speed.

What's your ph like? Have you been checking it daily?

Also what about your lights, are you sure they're enough? 4 cfls don't sound like much for 4 plants in bubblers IMO