Be careful where you buy your solar batteries

I started converting my house/office to solar power from 2016 on, for being a software computer systems analyst I need computer and internet access daily and the load shedding was negatively impacting my ability to service my clients. I initially purchased 4 sealed gel mat Narada deep cycle 200 amp 12volt batteries from the solarman outlet at Silverlakes Pretoria. These batteries are connected to my solar panels via an mppt charge controller purchased from solarman, being an essential component to correctly maintain the charge of your deep cycle batteries which should have a lifecycle in the order of at least 10 years. Within the first 1 year to 18 months all 4 batteries started failing. I took the first 2 badly performing batteries back to the dealer, who informed me that they don't cover the batteries under warranty and I should buy more batteries. I purchased batteries (different brand from an alternate dealer) which are still running perfectly after 2years. The batteries are not cheap as they retail between R4500 and R5500 each. I feel the batteries initially purchased could have been reconditioned as their useable lifespan declares this.