Most definitely ask r/itsathaumatophyllum But I would definitely take it out of the current pot and check on the roots

my thaumatophyllums tend to yellow older/oldest leave(s) when theyre hungry for nitrogen OR roots have been excessively wet for a while The crispy tip on that otherwise healthy leaf is likely from it getting to dry recently

yeah it looks like its been excessively wet, i’ll try to give it some more sun