i just trimmed off about 20 dead leaves so they look scrawny

http://img520.imageshack.us/img520/9907/dscf2424ec2.jpg

i started them in april. i could be completely wrong and not giving them enough as i am very inexpierenced i noticed last time i changed the water about a week and a half ago i cut the nuits back pretty hard 7tbs and the yellowing began again after the previos water change (they started doing well for the first time off 6tbs but they were smaller) also they seem to have grown less in the past week but im not sure. i progresivly added more in 1tbs at a time but they only got worse which led me to changing the water again today