To simplify interfaces means to consolidate and remove elements. Einstein said «Everything should be made as simple as possible, but no simpler.»
Removing labels from text fields is one of the things that make interfaces simpler visually, but harder to use. You lose a way to help the user understand the expected value (like an example of a Credit Card Validation Code «CVC») and you no longer see the label when content is filled.
Take this action
Add a label to your form fields. Use placeholder text to make the expected input easily understandable.