Thank You GPSFrontier for the valuable comments. Will work on the PH. As of today, the Lettuce has withered off and I am left with Bell Peppers. I will start another setup for Lettuce following your guidelines.
The sponge was purchased by a local hydroponics equipment manufacturer selling starter kits.
Your site
http://www.homehydrosystems.com/ is my bible and have the
nutrient requirement chart printed out for reference. I derived the need for PPM and PH from there. Guess its for older plants and for seedlings we should go by 1/4th rule
To give you more info of mysetup, here are the pics
For Bellpepper, I see a small root out of the sponge. Will monitor the progress and report back here.