What Am I Doing Wrong (Seedlings faded & dull) ???

I can help, ditch the rockwool cubes. Go with root riots or rapid rooter or other starter plug. Since switching from rockwool to those to germ and clone, I'll never go back to rw again.

Heated prop is your friend for seeds and clones too, don't let anyone tell you that you shouldn't use them. It's much easier to control the tiny environement in a propagator then in a room-temp/humidity for these stages. You don't have to, but when you use them properly you will get better results then any other method, IMHO. At least quicker germ times for seeds and faster root development for clones.

Vostok, I have to completely disagree with you about seeds having feed for 2-3weeks, that is inaccurate.

Try growing a seed in coco or rockwool for 3 weeks with nothing but water, it's not gonna happen.

In an inert medium like coco, rockwool, hydroton, etc, you need to start feeding almost immediately, just very lightly and work your way up. 3 weeks with no food? They will be dead by then, that's almost a month old!

After they sprout and have their first single blade set of leaves:

Week 1: 100ppm
Week2: 150-300ppm
Week3: 300-450ppm
week4: 450-600ppm

And up from there, depending on other variable such as strain.