overwatered plants dont usually go yellow,so its either plants are too warm,either too closed to a radiator or heat source or the light is too close to plants..remember to turn your arm over and you shouldnt feel any heat from light..humidity dome over plants for 2 days and keep misting the plant and top layer of soil 2 times a day..or nitrogen def. look for only rated 20-10-10 20 rates nitrogen.. only other thing is if your soils too compact the roots get no oxygen the plant slowly dies. IRISHHOMEGROWN is a good site for help..