Consulting the Codex…
RS3 · Skills · Activities · Quests
The Codex keeps its readings for 400 days, so you can go back that far, to the first day it read Knobb Cheese.
Defence 83 → 90, 2.6m XP
Herblore 90 → 96, 4.2m XP
Prayer 86 → 95, 5.1m XP
Summoning 81 → 96, 7.3m XPWeakest area: Potions. Herblore 90 → 96, 4.2m XP. Quests need a public profile, so the quest checks are left out of the score.