Here is the original item:
The potted geranium wilted
(A) from lack of
water on Terry's kitchen window
(B) while
the faucet dripped wastefully,
(C) staining
the porcelain sink with rust.
You wanted to do this:
The potted geranium wilted from lack of water on Terry's kitchen window
while the faucet dripped wastefully staining
the porcelain sink with rust.
The comma after wastefully is necessary. Staining the porcelain sink with rust is a participle phrase. Such a phrase will often require a comma when you connect it to the end of a sentence.
You might want to review the rules.