What would cause my vape to suddenly have a chemical type taste & burn my throat?

You are using the vaping machine for too long or if you have an adjustment to regulate the voltage is set too high.
The chemical you taste is the element running for too long and glowing white hot.
There are other factors but I have seen this myself and just replaced the element and the liquid which will be fouled anyway.
The base is common and I add my own flavors as required.
Vaping is to get the equivalent of tar from cigarettes into your lungs so the humidity is unnoticed. There is a vast science to this.
Advise if you require more assistance.