Don't give up yet. What you described were very good hits. I have no explanation for what went wrong. A double lunged deer goes down within 10 seconds (runs out of blood) but a single lung pass-thru will still give you a frothy arrow but only hit the near lung. If that first deer was slightly quartering to you this could have happened. One lung won't bring a deer down quickly. I'd recommend shooting at a 3-D target from all kinds of ridiculous angles, then study the path the arrow makes. Couple this with some studies of the anatomy and figure out all your angles. Remember that a sloghtly quartering deer may look broadside to you, the 3-D targets will help you with your shot placement.
BTW, I've not recovered enough deer to know how you feel, i felt bad and even felt like giving up. I'm glad to say I've not made any bad shots this year. But I only made one, a dead doe. I passed on many dinks,who knows had I shot a few more times I may have missed again. But I feel better knowing I didn't wound any.
Keep at it next season, do your homework and you'll get on track!