Cal-Mag is light on nitrogen at 2-0-0, so as long as you don't exceed the recommended one teaspoon per gallon, you aren't going to harm anything. I've used it in past to clear up calcium deficiencies with good results. Just mix up a one gallon batch and water as you normally would. If you run out, make another one gallon batch.
To elaborate on my first sentence, if your plants aren't suffering from anything that Call-Mag will clear up, it won't make them any worse and if you already spent the money on it, you might as well use it.
In any event, post some pictures and some of us may be to able to help some more.
Good luck and welcome to the forum!
I used a gallon on 20 plants, which is probably barely anything. I used the recommended amount per gallon. Here are some pics:
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