I thought it could be the characteristic of this kind, but it might already have been in bad shape when I bought it.
ご質問ありがとうございます。
"I thought it could be the characteristic of this kind"=「この品種の特徴かもしれないと思いました」
"but it might already have been in bad shape"=「でも、既に良い状態ではなかったのかしれない」
"when I bought it."=「私が買ったときには。」
ご参考になると幸いです。