I am also writing to Heartland to ascertain how they might resolve the issue.
Hi cdungan,
Welcome to the Heartland Owners Forum. There's a lot of useful information here along with a great bunch of people who are always willing to help out when needed.
Let me suggest that you call Heartland Customer Service at 877-262-8032. Have your VIN # ready.
If you've been on the road since May 2011 with a 2011 Landmark, you're past the one year warranty on the lights/lenses. If you send an email or a letter, you're very likely to get a response that says you're out of warranty. When you get on the phone, you might get the same answer, but there's a chance that personal contact may get you further.
I think Heartland changed suppliers on the 2011 fluorescent lights in mid-2011 due to ballast problems. If you've had problems with lights overheating and turning off, you might want to mention that in addition to the cracked lenses. I wouldn't be surprised if the cracks are a result of the overheating. Perhaps Heartland will give you an accomodation and replace the lenses or lamps. If not, they should be able to tell you if they have replacement lenses, or where to get them.
Btw, if you join the Heartland Owners Club, there's a 10% discount on parts ordered direct from Heartland. If you end up buying lenses, the savings might be worthwhile.