My first reaction is that this might not be diet-related, but that something else is going on that you need to check out. Just for the sake of your peace of mind, it might be a good idea to consult your physician.
As for the mineral supplements, have you had your blood tested lately (i.e., since going keto)? Do you have numbers to show that you really do need to supplement? A lot people find that if their salt intake is at the right level, the interlocking of the body’s regulatory mechanisms also keeps potassium, magnesium, and calcium properly regulated, too.
My personal bias is that our diet should provide what we need without supplementation, and there are data showing that a ketogenic diet can help the body either absorb nutrients better, or do more with what we get (depending on the micronutrient). Of course, there are always going to be people with special problems that require them to supplement, but my impression is that most of us should be fine with those minerals, if we get enough salt, which you clearly are. So, in addition to talking about the cramps, it might also be a good idea to check with your physician about whether or not you really need to be supplementing those minerals.
Vitamin D is a different matter, one I don’t really understand all that clearly. It is made from cholesterol, so if you are getting enough saturated and monounsaturated fat in your diet, you should have plenty of cholesterol for your body to use (cholesterol is the precursor of many hormones, plus being used in the brain and in the walls of every cell in our body). I understand that if we get enough sun, and we have enough cholesterol in our systems, we are probably making enough Vitamin D. But I would hesitate to tell anyone to stop taking Vitamin D who has a reason to take it. It is essential for bone growth and (along with Vitamin K) for getting calcium out of arterial plaque and into the bones where it belongs.