I'm trying the new upside down hanging tomato planters this year as seen in Birds & Blooms or on QVC. And, every one of my tomatoes (I think I bought Better Boys) have a dark scar over the entier bottom of the tomato. The plant looks healthy, & the 3 tomaotes I took off the vine were about the size of an egg, but, I put them aside & they actually turned red. But, what is the round scar-like thing on the bottom? It kind of reminds me of onion skin to touch, and there are several circles with-in the area. Any information will be appreciated.