How warm do they get the first time? Your charger might just be false peaking, which charger do you use? As long as they don't get too hot to touch at the end of the charge they should be fine.
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz