.empty-feedback {
    width: 100%;
    margin-top: .25rem;
    font-size: 80%;
    color: #dc3545;
}
.empty-feedback, .invalid-feedback {
    display: none;
}

.form-group.empty .empty-feedback,
.form-group.invalid .invalid-feedback,
.form-check.empty .empty-feedback {
    display: block;
}

.form-group.empty .form-control,
.form-group.invalid .form-control {
    border-color: #dc3545;
}

.form-check.empty label {
    color: #dc3545;
}