Instead of clicking on every plant/shroom/whatever u just stand next to group of ingredients and press (hotkeyed with number like spell or other items like weapon) scythe button and itz harvesting all of them for u with 'one slash' and after that in a blink of an eye u get message window with quantity of plants you were trying to harvest and number of ingredients u recived ( coz as well as I know the game mostly u get message that you found nothing to use on plant ; ) )
edit: I will turn off the mod and we will see if the scythe is the problem.
edit2: well it worked. Mod IS affecting that chest. It adds scythe to 'mychest'. Now FPS is back to normal : )
Thank you for your tips.