The two batteries will become warmer than the other batteries due to heat generated by a converter circuitry in the charger. This does not mean the batteries are charged faster than others or overcharged
The charger has a built-in converter circuitry that will become warm during rapid charging.
Occasionally, the charger might show blinking red right to indicate bad batteries. There are several ways to restore batteries that cannot be charged by the charger.If the light blinks red within five seconds after battery insertion, then the battery voltage is too high. This indicates that the battery already have a full charge. If charging is needed, briefly drain the batteries before trying again.
If the light blinks red in about 90 seconds after battery insertion, then the battery voltage is too low. Leave the batteries in the charger, while the light continues to blink red, for about 24 hours. Then remove the battery and try again.
Remove at least one of the batteries and the light will go off.