NY Section 8 & City Fheps vouchers

[Chryl Williams]

Good day all. I'm new to this site. My husband and I have been landlords in Brooklyn, NY since 2006.
We have great tenant of over 10 years that has had Section 8 since the beginning. Within the last 4 years, her husband obtained a City Fheps voucher and HRA shelter allowance payments. 
We have recently split the PLP meter so that the tenant would be responsible for there own utilities ( gas & elec) just like the other 2 tenants. 

#1 Can a tenant have all these programs making payments on their behalf?

#2 City Fheps has started making payments well above what the tenants owe. We get about $900 in excess. I've decided to put the excess in a savings account just in case the city realizes the mistake and wants the money back. The tenants claimed they went down to CityFheps to handle this but the city claims there's nothing wrong. 

Please advise on what we should do?

Chryl