[oldschooltech]

Hi. I have a Yamaha F310 8 years now and I've noticed that on the first few frets it seems to be fretting slightly flat. It's enough on the d and g strings to be noticeable when playing the 2 together. What could cause it to fret flat?

I've heard a lot fret sharp because of the nut being to high but I assume if it isn't buzzing then the nut isn't too low. Basically has anyone got any ideas of what would make it fret flat? The intonation is also a bit sharp at the 12th fret but I don't think much could be done about that.