Possible Calcium Deficiency?

Hey everyone.... So I am new to growing and am all of a sudden having some issues with a few of my plants. The background of it all is that I'm growing in a 4x4 tent with a 600watt light. I'm using DWC - 6 plants total - each in a 5 gallon bucket with a pump and airstones. I was going to switch to flower this weekend but now they are looking sick and I'm not sure why. I use Advanced Nutrients jungle juice. About 2 days ago the plants started looking a little thinned out and now the leaves are curling and there are spots on the leaves. Only 2 of the plants are having issues. The first 3 pictures are of White Widow and the last picture is of a Skunk plant. I'm thinking that it is a calcium deficiency but I really have no clue. Any help would be awesome. I have the PH and temp under control. Thanks guys!!

It's clearly a calcium/magnesium issue (yellowing at the top, brown spots on lowers). The ph would be the first thing to check. after that add calmag and don't go overboard.

It kinda looks like light bleaching. Im having the same problem now. Maybe your light is too close, its a common issue. If its not your light then I would agree with cannibal, ph issue.

I will get some calmag today. I haven't been at this long enough to try to figure out what the issues are yet by looking at pictures. Thanks!

I've had that before and the only thing I could find that resembled it was this description of "ph fluctuation." (<<link)

Calcium is orange/brown spots. Magnesium is yellowing between the veins. What you have looks like pigment loss. It's what mine looked like.

Thanks! It does look like the leaves are turning white. I will look into that as well. I did try calmag already to see if that does the trick.

Foliar calmag once at 2ml/L