I would guess a combination of problems. First, you are using pellets that are 7 years old. I would get rid of those right away. Pellets (especially if not stored in an airtight container) are notorious for sucking up moisture which then affects how well they shoot. It is very possible that you had a clean miss or two due to the old pellets. Switching over to a fresh can of loose powder will solve that issue.
It's also possible that you were not finding blood trails due to shot placement. Lung shots that are higher up tend to not bleed much right away, and sometimes don't bleed much at all. If you want to anchor the deer right away, go for a solid shoulder shot- you will probably ruin some meat this way, but most of the time the deer won't go anywhere. If you are confident in your marksmanship skills, a neck shot is another option.
Just because you don't find blood right away doesn't mean the deer wasn't hit mortally. Make sure you visually record the last place you see the deer as it is running away and the direction it is going. If you don't find blood right away, wait 30 minutes then go to the place you last saw the deer. Check for blood as you slowly follow the path it was taking. Eventually there should be at least a few small drops of blood here and there. Even if the bullet didn't expand, a .45 caliber slug through both lungs is going to kill the deer - you just need to find it.