My iPhone 6s screen is lifting towards the bottom, could it be battery swelling?

I have an iPhone 6s that I use for Zoom meetings, live streaming, and for social media. (It’s not my main phone.) It's in a thin rubber case and has fallen about 1 foot onto the wood floor a few times. I began to get concerned after finding out that screen lifting is associated with battery swelling. The phone overheated and needed to be cooled down during a livestream once. The battery health is at 100% and the phone is not slow. The battery functions normally. The phone functions normally overall. I have the phone in an otterbox case now to better protect it. I read that the older models have loose adhesive. However, I read that the 6s model is when the adhesive improved.