Yo dude those plants in the back look good.. how can this be are they all gettin same feed?? if it rains alot dont water plants until the soil drys out.. if you top the plant you will get two main colias instead of one but this should only be done in the veg stage not the flowering stage.... since you have seaweed and manure in the soil this could be causing the problem but im not sure.. these could be overfeeding your plant.. hopefully someone else here with more experience than myself can help ya out..