Not sure which is the problem, either the Reds aren't dropping hides (getting 2 every 24 hours) or the dragons that drop the hides are not regenning. There are 7 red dragons that can regen:
Red Dragon Hatchling, Mob # 195 drops nothing
Baby Red Dragon, Mob # 182 drops a tail 1%, Mob # 1107 drops nothing.
Young Red Dragon, Mob # 183, drops red dragon hide 1%, Mob # 1106 drops nothing
Adolescent Red Dragon, Mob # 184, drops dragon fang 1%, Mob # 1105 drops nothing
Getting plenty of tails and fangs, but 2 hides every 24 hours is way off. So either the engine is genning the # 1106 Young Red Dragon excessively or # 183 Young Red Dragon isn't dropping them as it should.