You may have needed extra salt, magnesium, potassium, or even more water.
Have a google for the signs of deficiency for mag and pot, and see if they ring any bells.
I supplement with them, particularly in hot weather, and feel much better for it.
When we switch to low carb (esp ketogenic) our kidneys change the way they function a bit, and they flush out salts and minerals as well as water, in a way that they don't when we are eating plenty of carbs. In addition, a lot of the carby foods like potatoes and rice and bread have a lot more salt in them that you might expect - and those disappear from the diet.
Several of the LC experts, like Voleck and Phinney recommend that we make broth, or use good quality stock cubes in hot water as a drink to replenish these minerals daily if we low carb, and I have certainly found in beneficial.
Amazing to think that being short of such things can make us feel so floppy and listless and apathetic, but my own experience backs it up - especially in hot weather.
You comment about needing more fat is also possible, but depends on whether you were losing weight? If not, then you were getting enough from your diet.
If you are intending to LC seriously, and look on it as a lifetime way of eating, I heartily recommend the Volek and Phinney book I list in my signature. It debunks most of the myths, and gives fab info on how to avoid most of the easy mistakes.