Watering schedule for hydroponic tomatoes

[Kevin]

Hello I am currently growing several varieties of tomato plants, ranging sizes from 4 inches to 2 feet. I have noticed that recently, a lot of the branches are starting to curl under. Everything else appears normal. I am watering on 30 minute intervals, using one of your systems that I built last year. Does this sound like over watering? I have them growing in a greenhouse.
Thanks, Kevin