Hi Tom,i would appreciate your advise cause i seem to get all sorts of advises.my tank is 29g,2x28w t5 bulbs 7hours per day,i dose 24ppm of N03,24ppm of K,2.1ppm of P04 and 9ml of flourish throughout the week,on and off days and 60% weekly water change,i dose co2,kh is 3.5 and ph really low around 6 maybe less.no animals in the tank.my plants seem to be yellowish and cabomba stems are long with a long distance between leafs.the light can reach well to the bottom of the stems.i know there maybe be lots of factors causing this but what is the most reasonable explanation so i have something in mind?thanks a lot..