Should I flush Them Or Add FF Grow Big

I transplanted them two weeks ago and their six weeks old yesterday. I actually flushed them a week ago cuz they we're really dark green, a few shivled and died, im assuming it's a Phosphate defincency their looking better now just a few leaves still dark green but was wondering should i flush again or add nutes i have them growing under 6 four ft 40 watt cfl's and I use publix drinking water and add couple drops of ph down it has a ppm of 220

if you want them to get bigger keep feeding them nutes or start the grow big and throw them in 12.12