Yes, under certain circumstances, your parents can receive a deferment on their loans.
If they temporarily can’t meet the repayment schedule, they can also receive forbearance on their loan, as long as it isn’t in default. During forbearance, their payments are postponed or reduced.
Generally, the conditions for eligibility and procedures for requesting a deferment or forbearance apply to both Stafford Loans and PLUS Loans. However, since all PLUS Loans are unsubsidized, your parents will be charged interest during periods of deferment or forbearance. If they don’t pay the interest as it accrues, it will be capitalized (that is, added to the principal amount of the loan, and additional interest will be based on that higher amount).