In game freezing?

*randomly in game i will just freeze for like 2-3 solid seconds......

*as far as i can see, some champion skins are making this problem even moreso worse

*this problem has been going on for 2 months now and gotten progressively worse

*ive played league on this computer for well over a year, never had so much as stutter in terms of lag

*my internet is 100% not the problem

*no slowdowns or anything weird happening in anything else im doing and only league

....anyone got any ideas on a fix?