There are many possible reasons. I tend to find that many managers start the season cagey, looking for position, before becoming more aggressive later as opportunity allows. Maybe your Hard Attacking start is suffering in the face of more counterattacking opposition - but it could be anything.
I have in the past (and I go on about it a lot

when the opportunity arises) had 1 season where I failed to win a single home game in the first half of the Season (but won through on the last day). Never really thought that I found the answer. I just drank the Champagne and got on with the next one.