why does my iPad Mini 1 have trouble running games?

my iPad Mini 1 has been good to me for the last year, but I've been noticing terrible lag while playing games such as Modern Combat 5 and Dead Trigger 2. I've completely restored my iPad so nothing's on it, turned on reduce motion and reduce transparency. I also turned off background app refresh and automatic updates Just to see if I can get games to run without struggling so much. I usually never have any apps open in multitasking.I restart or reboot my iPad before every time I do a game. My iPad Mini used to run games just fine a year ago, but now the lag is making games not enjoyable.