brown on the bottom of my tomatoes

[Mike C]

Hi Ron, I have a General Hydroponics Aeroflo#40 and I have Beefsteak tomato plants that were put in on March 8 and I cannot believe how fast these things are taking off and I had been using Dyna-Grow and Earth Juice Catalyst for about 5 weeks and then I read where you using Miracle Grow for tomatoes and Epsom salt so I changed over and the plants really liked the change. They are over 6'tall as of today and they are real healthy with one exception the lower tomato sets have brown on the bottoms,but not on all of the sets even on the same group. I keep my PH at an even 6.2 and measure it every other day. I keep fans running all the time to move the air and to keep the humidity down. The plants are using or moving about 7 to 10 gallons of water per day. Any suggestions? Thanks Again
Mike from Mo