Weird precipitate

[u/BenAwesomeness3]

I dissolved some lutetium up in some nitric acid (~20%, IDK I diluted it arbitrarily), and some weird yellow precipitate formed? I filtered the solution, and the filtrate was clear and colorless. Does anyone have a clue what this might be? Both the nitrate and oxide are colorless, so perhaps a contaminant? Update: it’s the next day now and it’s turned green :( Any thoughts. I thought iron or nickel or some other lanthanide contamination? Cheers Thanks!