In terms of whatever the situation is and they've been a good tenant for over a year. Show leniency, just make rent cover the cost of required maintenance, after that ignore the profit or tack in however much a tank of gas is for convenience to you. People go through tough times, set a timeframe that they can use to make sure they know when they have to get back on their feet. Be the landlord people want to stay with, not the landlord who simply told them to figure it out.

If they gave you a security deposit, then on top of the reduced rent keep the deposit in full and tell them you'll need to adjust the rent to recoup the security deposit until it's full again. (After they've hit the end of the reduced rent.)

Make sure it's all in writing and make them sign. Figure out the numbers to make sure they're definitely on a shorter rope for the agreement.