calcium problem

I am growing in a dwc set up and my plants are showing signs of calcium deficiency(this is my first hydroponic grow). I am using RO water. What would everyone suggest I use to get them some calcium? Some are in flowering so I don't want to mist them. Other than this they are very strong and healthy. Thanks

Go buy Cal/Mag like 11 bucks. 1 teaspoon per gallon I think.

I went and got some today. Thanks.

u can also use vinegar

vinger? what amount?

1 tea of hydrated lime per gallon of water. that will clear it up man.

Here are some pic's. The last shot sort of shows the lower leafs. Like I said it's not real bad. They are 13 days in bud.