My father died due to covid

You have no legally enforceable debt for the 3 cheques issued by the deceased.

Verify authenticity of promissory notes. However, no one can attach property devolved upon the legal heir of deceased without specific orders of competent court.

It is better to consult and engage a local prudent lawyer for appreciation of facts / documents, professional advise and necessary proceeding.

What is the occupation of your father, and his relations with claimants on such borrowings?   These facts must be studied in-depth?  A competent local advocate who is competent to study the facts as per promissory notes and account books or entries in diary etc of your deceased father.  If your father is in business.  contacting employees, partners, bank accounts may help you.  The most important evidence is whether your father needs such borrowing really or not.  (In one case a relative of deceased has produced a promissory note that deceased has borrowed Rs.25,000/- @ 18%, whereas the fact as per account books is that he always maintained lakhs of balance in the current account have lakhs in fixed deposits and his cash credit with 15% interest was used very sparingly, and the fact is that he never needs such amounts and when the promotes were sent for comparing signatures, the opinion is that promote was forged)

.  It is the duty of your advocate to disclose facts that you are not aware of, no knowledge of such borrowings. and seek all supporting documents as xerox copies. The notice must be issued in a balanced tone.

All Legal Heirs  are liable for the debts made by the deceased Father to the extent of respctive shares in the property being inherited.

However, please ensure genuineness of the claims being made for which notices are issued to you and other Legal Heirs 

First of all, ascertain the genuineness of the demands, and take steps to settle the genuine ones. It could be that cheques and promissory notes relate to the same transaction.

As regards those which are not genuine, reply to the notice accordingly.