I had a rude awakening this week. Two of my tomatoes looked like this.
When I cut the tomato open, it looked like this (blech!)
Naturally, the first thing I thought of was that bugs had gotten into the Aerogarden. But to my relief, after a few searches on Google I realized that this is something called blossom end rot.
It's a natural disorder caused by a calcium deficiency. According to Colorado State University, it can be caused by a "combination of cold temperatures or excessive heat during blossom set, and fluctuations in water supply". This makes sense--the heating in my living room is not the greatest, so the Aerogarden has probably been subject to extreme cold with all the snow we've had this winter. Also, there are times I do let the water supply get too low. Finally, I have been using Aerogarden liquid nutrients for herbs--perhaps they don't have the same calcium content needed for tomatoes.
Anyway, I'm fixing all three elements, and we'll see how it goes.