What is the EFC for your two other children?
I haven’t had two or three kids in college at the same time ( so we’ve actually spent more than we would have otherwise), but with before tax income of $140,000, I would expect FAFSA EFC, to be at least $30,000, if not more, because it is often 1/3 of before tax income of over six figures, and 1/4 of before tax income for earnings of less than $100,000.
If you are self employed or have properties other than your residence, that won’t be the case.
This guide shows the calculations behind the EFC,
http://ifap.ed.gov/efcformulaguide/attachments/090214EFCFormulaGuide1516.pdf
As it does sound like something is off, but in my experience, college financial aid officers will correct your FAFSA, if something is wrong. ( although, they aren’t always correct in doing so)
Are your older kids getting need based aid from state schools?
If so, I would agree with you that it seems your next child in college would be eligible as well.
Especially if you then would have three kids in undergrad schools.