经过几周的进步后，孩子的语言能力又退步了。

After weeks of improvement, the child's language skills ___regressed.

他的数学能力退步了，现在连简单的题目都不会做。

His math skills have ___regressed and now he can't even solve simple problems.

在分析过程中，模型的性能指标出现了倒退现象。

During the analysis, the model's performance metrics ___regressed unexpectedly.