AC Needs Upgrade No or Go?

[Ernest Somereve]

So I just recently purchased a duplex back in May of this year, we have inherited the tenants who have been there for years and they seem to be good and even paying rent early. One of them brought it to my attention that the AC system is not keeping the house cool and they wished to put in their own window unit. We live in Florida and its the middle of summer and it is brutally hot outside 90+. The AC system was installed in 2017 and our licensed home inspector checked it out and said it was good. I sent an AC company out there today to check it out and see if was a simple fix however, he stated that it needed all new duct work and blown in insulation to the tune of $5000.00. The tenant said the previous HVAC company that the prior landlord had also stated the same thing. Just to be clear current rents are approximately $300-350 under market value and I'm not sure if they would be willing to pay the increase.

My question is do I:

A) Bite the bullet pay the 5k

B) Get a 2nd opinion

C) Leave it the way it is

D) Wait for this tenant to move out before replacing it

Thanks for any suggestion!