New-ish tires almost bald on both front inner 2-3 inches, what's causing this!?

I have a 78 Fiat X-1/9 Bertone that I recently got out of storage. It sat in the Phoenix, AZ baking heat (car cover did not cover tires) for 18 months. Now it feels like it's going over slight bumps in the road all the time, AND the new-ish tires are severly worn on the front (inside) Did the tires get melted flat where it sat for so long? I don't think I've got even a couple thousand miles on them & I think they may need replacing already ! they are alarmingly worn on the inner 2 inches--as in almost no tread depth --ie almost bald! (insert swear words here--the tires weren't cheap!) Any ideas?