In my experience as a band director (retired) and a tuba player, the tubas tend to sound sharp, even if they are supposedly "in tune". A very wise director told me to tune my tubas 5-10 cents flat. That doesn't address the notes you mention, but it will help, and improves the band's sonority much more than you would think. The 2nd & 3rd valve combinations tend to be sharp, anyway. In that case, I pull the 3rd valve slide about a half inch and let it stay there. That will make the 1st & 3rd combination slightly flat, but if the tuba has a 4th valve, that's not a problem, anyway. On the 1st valve notes, different tuba manufacturers try to make that slide where 1st & 2nd combination is not so sharp. Best wishes.