lack of firwood after upgrading woodcutters

Hello
I just upgraded 6 of my firwood cutters, so i got a total of 8 cutters at lvl3. But since i upgraded them i'm permanently out of logs. Before upgrading i had 4 cooking plants (lvl 3, 3, 3 & 2) running all time. Now i barely can afford 2 running same time. :confused: That can't be! pls do something about this!

check your production chains in a simulator, you may be over harvesting your trees since you do not mention foresters here.

(and donate to the author if you like the sim)
http://ceo-economy.appspot.com/