Resource Pack Lag

I'm experiencing extreme fps drops and lag spikes whenever I use the server resource pack. When I play without the pack, I have a smooth 70+ fps. When I do play with the pack, my fps drops to 30 for the first 5 minutes of game play, but after the 5 minutes I go back up to 70+ with lag spikes that drop my fps to 0 every 30 seconds. Anyone having the same problem?

As an additional note, through the help of friends, I managed to acquire Wynncraft's resource pack as a separate download. When I loaded it up in the main menu, the resource pack still lagged me horribly there too and this was just in the main menu. I won't share where I got the separate resource pack in case of some weird rule or something that could get me banned.

 

Use f3 and check the top right to see if your memory is capping. If that's the case, allow more memory in the minecraft launcher (It will only longer the delay) but there is no way I know of to fix it. It happened to me without the resource pack, but no longer happens now, somehow.

If that's not the case, I have no idea what could be causing it. Maybe try lowering your graphics settings or using a better computer. I get like 15 fps anyway.