Maybe I'll stand corrected.In my limited experience with CE4's, yes- I had the same problem and all the juice was tainted- but then, I can break/render unusable any vape equipment just by looking at it, so I'll happily be corrected by a more sensible ape!!
Only if you seriously cooked the coil in the e-liquid
If the juice goes very dark in a short time after/during vaping, in the ce4, what does that mean?