looks like you have a few things going on but the yellowing is a n deficiency.your ph in soil i believe should hang anywhere from 6.2 to 7 or so i believe 6.8 being the spot to keep.you need to get your "n" up for sure that will fix that problem.now the brown spots on the end of the leaves that looks to be nute burn.many things can cause this also,like spraying your plants down with nutes or water and the lil droplets of water act as magnifying lens and this can cause burns in direct sunlight.but it looks to be nute burn.


hope this helps