When the first fruits begin to appear it is always a good idea to remove all leaves below the first truss so this should also help your problem. A normal tomato fertiliser should also be useful if you have problems with epsom salts or if you are organic then I believe comfrey leaves placed around the base will do the same trick.
I'm growing tomato plants this year for first time. About twenty, all at different stages.Tomato plants like heat and light as well as water and feed. Adequate support too. I gave one to my sister (it's indoors on windowsill at 24 degrees c..some like it hot!).It has produced about 40 little tomatoes ..most are green at moment.All of my plants are outdoors (average temp about 10-15 c and are just at the flowering stage.(Glasgow).
I hope weather get's better. HB