Weak can mean a few different things
Different vapers mean different things when they say a kit feels weak. Some mean the nicotine is not landing the way it used to. Some mean the flavour reads quiet. Some mean the cloud is smaller than expected. Some mean all three. The good news is that the variables behind each one are short, well understood, and adjustable. The fix is almost always a small change rather than a whole new device. Working through them in order is the fastest way to land at a kit that feels right.