Are the marital problems experienced by a woman with psoriasis, who did not inform her husband of her illness before marriage, considered a punishment from Allah, and what should she do to repent?

If illness establishes the right to annul the marriage, then the husband must be informed of it; otherwise, not. The corruption of life is often caused by sins and transgressions, so the questioner and her husband should increase in repentance and seeking forgiveness, engage in self-accounting, rectify what has been missed of obligations, and avoid what is forbidden, so that Allah may mend their condition.