All I can say at this point is that some condition or component is causing the esc's to fail. Either too much heat or too may amps. You can get a higher rated esc and install it but I would either buy or borrow a watt meter and test the set-up before running a battery through it again. It could be the connections, the prop, or it could be a failing motor. You really need to see how may amps,volts, watts, etc... the set-up is drawing at no-load and under-load Otherwise it is just a guessing game.
Also , I''m not a fan of running a Lixx battery down to LVC . The LVC is there as a safety but I bring my boat, planes, helis, in when the packs are at 3.5v/cell by calculating and setting the timer on the transmitter. In my opinion when a pack is constantly run down to 3.3v/cell under load it is slowly damaging it and that is how they eventually puff and fail. I have packs that are 5+ years old and still have good internal resistance and put out close to their C rating while I've had in the past packs that were run to LVC and in a short period had high resistance ,puffed, and had to be disposed.