The new Cohesive Gel Implants remain equally cohesive under normal body temperature. It would take temperatures above those consistent with life to break them down.
All of your symptoms align with evidence of a spitting suture or stitch "popping out", which is a very common issue following a breast augmentation surgery. Some people are more sensitive to the absorbing sutures and can push them out of the body resulting in the reaction that you have been ...
Unfortunately without at least a picture or breast measurements it is impossible to say whether 400ccs is too big. If you are still in doubt then I recommend you seek a few more opinions with Board certified plastic surgeons who perform a lot of breast augmentations. Best of luck to you