First of all, huge thanks to the website creators!
Please tell me (I'm playing on Hero difficulty, version 1.6): on month 2, week 1, day 1, the cost of all magic spells increases by 2 times. For example, creating a phantom used to cost 18 mana, but now it costs 36. This increase happens for both Agrael and my other hero. I also noticed an increase in the cost of units - dryads, druids, cave demons. Is this supposed to happen?
If so, will the normal cost be restored in the next mission?
If not, what is causing this and how can I fix it?
I really need an answer! Thank you in advance!

I had a week like that, it's really tough, especially if you have few knowledge points, you won't be able to use mana much, it's the same as getting a week of Recklessness, when the experience gained in battle is reduced by half, you might as well just lock yourself in the Castle for the week and not go out, because there's nothing to do)) unless you have free resources collected.