Is there a such thing as a math deficiency?

Yes. Dyscalculia = . Specific Learning Disability with Impairment in Mathematics. Lack of understanding of quantity impairs learning to count in pre-school, comparing numbers in KG & linking written or spoken numbers to quantity in school. IQ is avg. to above avg.; problems with time, measurement & spatial reasoning often co-exist. 3-6% of the population has dyscalculia; 25% of people with dyscalculia have ADHD. .
NO. NO- some people, myself included, are not good at math: a college student who tutors will help immensely.
Yes. I would not call it a deficiency, but we are not all the same when it comes to math, or for any other subject. Math is typically a right brain spacial subject while language is left .
Unclear. Please clarify what you mean by "math" deficiency. Do you mean something to do with arithmetic or are you thinking of a slang word, "meth" for a drug?