I'm going to repeat this again, not against anything that has been said but in the name of common sense. You can't tell by guessing if you have too much or too little of an electrolyte. Yes, Pred can deplete potassium but health situations are complex, with many things coming into play like other health conditions, drugs (like Benadryl), diet and metabolism (and lovely things like capillary permeability). So please check with your doctors before you do anything that could send your MG downhill.

If you have any kind of kidney issue, which Lizzie is very aware of, too much potassium can cause the same spasming of muscles. And you can have too much magnesium then too.

Any new symptom should be told to your primary physician and/or your neurologist.

I had an overload of potassium, due to retention of fluid/electrolytes, and it affected my heart to the point of feeling like it was going to stop and needing to go to the ER. PLEASE do not take too much of any electrolyte. Too much calcium can lead to kidney stones. Unless you've had a problem with "electrolytes" I can understand that it would be easy to pooh-pooh their impact on your body. It's not fun and can be very dangerous.