"Tapos" means "finished" or "the end of an event". Another word, "pagkatapos", is often shortened to "tapos" and that's the one Neil commented on as used when narrating a series of events to give the meaning of "and then" or "afterwards". "Iba" means "different " and in a sense can mean "another". When used together as "tapos iba", it would be the clipped version of "pagkatapos" that is being used there. Hence the phrase would mean, "and then different" or " and then something else". When used in a sentence, it indicates a contradiction of events or ideas. Examples: Ito ang sinabi mong gagawin mo pagkatapos/tapos iba ang ginawa mo. = This was what said you'd do and then you did something else. Sabi ni John mahal na mahal niya si Mary pagkatapos/tapos iba ang pinakasalan niya. = John said he loves Mary very much and then he went to marry someone else.

Tapos is sometimes used as 'Then' like 'I got there, then I spoke to her' (dumating ako, tapos, Sinabi ko sa kanya' or something like that. Maybe that can help you in your context.