It sounds like a classic case of cold temperatures. Cold can cause the leaves to turn white. It may delay plant growth, but, providing the temperatures pick up and return to normal, it ought not to prevent further development. I presume, of course, that the plants that you bought as well as the ones that you raised from seed, had been hardened off before being planted out. If not, then the cold would have been the result of temperature shock.
With regard to "pinching out"tomatoes - it all depends on the type of tomato that you are growing. Those which are best trained to prevent them from using up their energy in side shoots, should have the shoots that develop where leaves branch from the main stem removed. Bush varieties can be allowed to develop naturally. (I find that such tomatoes, Gardeners' Delight, for example, benefit from a bit of training at the outset, so that side shoots are removed, and allowed to develop naturally later; this makes it easier to ensure that watering reaches the roots and splashing of lower leaves is less likely. Others may disagree: gardening is not an exact science!).