Talk to your ped. and see what they recommend.
My LO was drinking Enfamil Gentlease since birth and at around 4 months, he started to get a rash all over his body. After ruling out eczema, his ped. recommended we use Nutramigen and the very next day his rash was better.
How about starting with a soy based formula? I hear a lot of babies do well with soy formula- especially when their tummies aren't tolerating other formulas.
I wouldn't try Earth's Best again if I were you. A bad reaction twice is enough for me not to try something again. And just because its organic doesn't mean its the best thing for YOUR baby. Nutramigen is milk and soy free and its hypoallergenic (expensive too!)
Anyway, hope this helps.