3週3日目 かじったとたん
Development・time・result
接続：普通形＋かと思ったら
As soon as I thought A, I immediately B
注意 / Note：とたん is an immediate sudden change; あげく usually ends badly; 末 is the result after long deliberation; かと思ったら emphasizes two things that follow very quickly.
比較 / Compare：Same article: 〜たとたん（に）／〜あげく／〜末に. These models are often mistakenly chosen for each other — carefully read the 接続 and nuances above and then decide.
よく出る形 / Common form：普通形＋かと思ったら、〜。The speaker OBSERVES other people, so he does not use it for his own work. The voice was surprised because it changed so quickly.
泣いたかと思ったら、もう笑っている。
As soon as I finished crying, I immediately laughed.
雨がやんだかと思ったら、また降り出した。
Just when I thought the rain would stop, it rained again.
静かになったかと思ったら、また騒ぎ始めた。
Just when they thought it was quiet, they started making noise again.