Visitor Visa - B2

Hi Everyone,

Requesting some advice on B2 visa rejection for my parents. I live in US on H1 along with my wife and kid. I had applied B2 for my parents and it got rejected last week at Chennai consulate. My father works in a private textile company and my mother is a house wife. Below are the questions that were asked in the interview.

1. Why do you want to visit US?
Ans: For tourism and to visit my son and his family.

2. What is your son doing?
Ans: My role and organization.

3. Where is your son living in US?
Ans: City and state.

4. For how long you want to visit?
Ans: 3 months.

5. Is your son married?
Ans: Yes.

6. Does he have a kid?
Ans: Yes.

7. What is the age of the kid?
Ans: 2 years.

8. For how long your son is living in US?
Ans: One and a half years.

9. What do you do?(to my Father)
Ans: Fabric coordinator in a textile company.

Then the officer issued a 214b saying the Visa has been rejected and details are in the sheet. Did not ask for any document from my parents.
I am clueless about the reason for denial here. Have they rejected it purely based on something in the DS-160. For the question, Have you made specific travel plans, I had mentioned as No and intended period of stay as 3 months. Is this an issue mentioning specific travel plans as No. I couldn’t find anything else wrong in DS-160. Can someone please help me if you find something wrong or a reason that could have caused the rejection. Also if I wish to re-apply, is 45 days gap sufficient or should I have to wait longer. Please advice.

Thanks in advance.