Sunscald will turn the green trunk/branches to a brownish color. I have one in my yard now with a branch that has it... if I get a chance I will take a picture to show you.
If you prune and shape your trees properly, you won't have to worry about it long term. You should have leaves that create a nice canopy to shield the trunk and branches. The biggest risk is for young trees. It can lead to fungal issues and branches to die. IV organics has a 3 in 1 with a green, brown, or white color that is an alternative to the white paint. It also is supposed to help stop rodents from gnawing the bark (if thats a potential problem for you). Its a bit pricey though (~$30 for a pint I believe). There is another thread here that is talking other options, you may want to read through it.
Defoliation is normal as trees grow. I'd just give it some time and you should probably see some new growth soon, assuming they are correctly watered, fed, and the weather is cooperating.