The second and third are small, but the majority of how blocks are generated is random so it's just something we have to deal with.
The second includes transactions with 1.25 Sat/Byte, so my guess is mempool was as good as empty after mining this block.
Unless there's some part that isn't automated and is tryiong to push the fees back up of course because they have gone quite low recently.
F2Pool doesn't include transactions with less than 5 Sat/Byte fee. Fine with me, other miners gladly took my $0.05 fee today.
