Tenants want out of lease because of roaches?

[Tatiana O'Hara]

I have tenants living in a townhome in Georgia. From the very beginning they've been a headache and I should have walked away.. They started a lease and canceled it same day prior to moving out. I let them break the lease by forfeiting the security deposit. They call back later the same day and want to start a new lease.. again, shouldn't have done it but I did, and made them pay first and last up front. Anyway, they show up to move in and find a few dead bugs. I sprayed the home prior to move out so I assume that's why. The home is in front of a retention pond so we get occasional small red roaches/beetles from that. Not to mention hot humid summers in the south. They complained so I immediately had it professionally treated and I resealed the patio door. This was all within the second half of May. First full months rent (June 2019) took the entire month to collect. The man of the home is a total con artist. Tons of back and forth about the rent, and he would always bring up small issues like  the fridge wasn't cleaned or the towel holder is loose. I serve a pay or quit notice and they finally pay. The woman of the home occasionally text me saying she saw a dead bug and throwing around the word infestation, so I have them come out to spray again. Both times the technician said there was NO sign of infestation. August 1st rolls around and the man says rent will be late. He understands the late fee and we agree to meet 8/10 for the rent. He shows up with printed emails to prove he has a 20k check being deposited and will have it the next day 8/11. I never get the money... I text both of them like what's going on and they say they will have it monday but I should cut them a break since theres a roach infestation. They keep throwing this word around but I've spoken to the neighbors on both sides of the unit and they've had no issues. The woman even told the pest control guy that the issue was on the main level. I had the door PROFESSIONALLY resealed this time and the tree trimmed that might be helping them get in. Mind you the lease says tenants are responsible for pest control. We are meeting tomorrow for a mediation meeting and she's supposed to be bringing the rent with her. She claims they want out because of the roaches but I think it's because they can't afford the home. Can they sue for inhabitable conditions? They are saying the issue was preexisting since they aw dead ones but I lived there 2 years and never had a problem. I told her to break the lease they need to pay 50% of the remaining term as their lease states and now they want to get a "lawyer" which I think is a scare tactic. Also do 
I have more leverage due to their payment history? I'm new to this obviously.