There are a LOT of ways to deal with low grades. The first thing that is great is that your UG grades (which are in fact more important) are high. Which means you may not even have to explain away anything at all. If your grades are BAD, maybe, but if they are average, As for the time you took, in general, up to a year more would be acceptable, any more starts to raise questions. Better to leave well enough alone.
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