that sounds like a lot of tomatoes in a small area...............did you amend the soil, does it have old cow or horse manure mix with some lime in it.................you could try to put a small amount of this mixture around the edges of the planter. we had a lot of rain this year............I had brown leaves on the bottom of ours.....I carefully trimmed them off and cleaned the knife......are they getting full sun....are they in heay wind.....next year can you plant them in something deeper or put them in the ground......