I don't see any decline in performance from Leverkusen, I think the two draws they got are quite normal because they were against strong teams in the Bundesliga and also Xabi Alonso made several player rotations because the brand no longer has any interests after successfully ensuring the Bundesliga title in These two matches Leverkusen showed something extraordinary when they scored a goal at the end of the match to avoid their first defeat this season, I watched these two matches and I couldn't believe what I saw, it was truly extraordinary and I thought the Leverkusen team didn't will be defeated this season.
Being draw is normal result for Bayern Leverkusen after winning Bundesliga tittle and Xavi Hernandez make many rotation since after winning Bundesliga after beating Werder Bremen on games week 28. Its not much problem although got draw because Bayern Leverkusen save their player for Europe League match and won't loss bigger opportunity for treble winner in this season.
Last two match with draw result, Xabi Alonso make some rotation and most of key players put them on the bench, its not really crucial although Leverkusen failed to defend the unbeaten record because their have reached target after winning Bundesliga tittle and focus for upcoming match in Europe League and save the main player for DFB Pokal Cup final match.