I am not very familiar with KGo, but for me, when it comes to my e-cig batts, and seeing that they are constantly near and in contact with my face, when they show signs of malfunction, I toss them. That might not be what many do, but for me, I do just to be on the safe-side as it is in no way shape or form worth it to me to salvage some money only to have a potential fire start, or worse, with a batt that is not working properly. It is the fact that your cartos are getting discernably hotter than what you are used to and the burnt taste that would give me pause with that particularly batt, not just the fact that it is losing its taste and vape so quickly. I have had the latter happen with certain juices rather often and not due to the batt.
And that is what I always advise to others, but obviously each person is free to handle it how they feel best and I am thin skinned enough to handle criticism to my post if it comes. In your particular case if I suspected the issue was due to the type of juice I was using, I would get a fresh spare batt of similar model, and try that to see what happens. If similar issues, I would chalk it up to the juice and go from there on a work around and not trash the original batt. But I just would not auto assume it was the juice causing it to burn thru cartos that fast.
I've had issues in the past with rechargeable batts causing a fire when they were not performing well (usually while on the charger). Luckily never with an e-cig batt, but rechargeable batts are similar in nature regardless of what type of unit they are in.