You did not say what you were using as your fertilizer or if the plants are growing fast or slow or have big leaves or small leaves etc!
Or what color the leaves are etc!
The reason for the bugs may be that the plants are not getting enough Electrical Energy release from the Acids of the Phosphate area against enough of the needed Alkaline Minerals!
But I can not tell without some more info as just where your plants may be with the info which you have given!