If you used Simple Green, instead of Extreme Simple Green, you need to go back and make sure that you rinse off every trace of the cleaner. Simple Green will attack aluminum if not rinsed off completely from every crack and crevice.
Extreme Simple Green is designed for aluminum and is available online or Home Depot.
I should have added the link from Simple Green:
Questions about Simple Green(Click on Aluminum)Here is a highlight from that link:
However, caution and common sense must be used: aluminum is a soft metal that easily corrodes with unprotected exposure to water. The aqueous-base and alkalinity of Simple Green All-Purpose Cleaner can accelerate the corrosion process. Therefore, contact times for unprotected or unpainted aluminum surfaces should be kept as brief as the job will allow - never for more than 10 minutes. Large cleaning jobs should be conducted in smaller-area stages to achieve lower contact time. Rinsing after cleaning should always be extremely thorough - paying special attention to flush out cracks and crevices to remove all Simple Green product residues.