What causes this?
 

Hi all. I have to phalaenopsis orchids that continue to have the mottled look to their leaves. When I posted about this earlier it was suggested that they had a calcium or magnesium deficiency. So I went and bought some Cal Mag and have been using it weekly with every watering. Don't know if the pics show it but the older leaves are much more pronounced than the newer leaves which tells me there's been some improvement. I'm guessing the older leaves will not go back to their normal color, but I see a slight bit of it in the new leaves. This phalaenopsis is grown in straight medium to large chunk bark. It is 1 of 13 that I have in my light Garden that I have posted pics of in the past. This orchid has bulbous growing roots, and is coming out with a new Leaf again. Other than this strange discoloration of the leaves it appears to be quite healthy. I am confused at what the issue is.

Phals are not silk flowers and all leaves on all plants do not look alike. I see nothing in your photos that I would consider out of the normal range of leaf patterns. I will warn you that using cal/mag every week may cause more problems than you think you have.

The old leaves won't heal, so keep track of the new growth to see if it starts developing any problems.

Good to know cymb. I'll cut back. Currently I've only been using 1/4 tsp. Per gallon...

Calcium helps to form the cell walls and membranes so once these are formed, the cells cannot use any added Calcium. That is why adding Calcium just before or during growth is so important.

well they are all still definitely in a growing phase.

Magnesium is incorporated into chlorophyll. Yellowish leaves and streaks can be caused by magnesium deficiency. Red spotting on Vandas in cool weather can also be caused by magnesium deficiency. It can take months to replenish plant stores of this element. The Vanda alliance, which includes Phalaenopsis, seems to need more magnesium than do many other orchids.

Old leaves continually replenish chlorophyll destroyed during photosynthesis, so treating a magnesium deficient plant can cause old leaves to green up, too.

Is there something other than cal-mag that I should use?

There are all sorts of things you can use. I use Epsom salts bought at a drug store for magnesium. I add 1 teaspoon / 5ml of powder to 5 gallons / 19 liters of water on my Vandas every 1-4 weeks during growing weather. Other people use more or less.

There is a lot of calcium in my tap water so I mix my tap water with rain water. How much calcium is in your water? Maybe you don't need to supplement calcium.

I have no idea how much calcium is in my water. I have a gravity-fed well, and use this well water on all my plants.

---------- Post added at 10:29 AM ---------- Previous post was at 10:28 AM ----------

Surprisingly, the plant that I took pics of is now spiking for the first time and growing a new Leaf. Apparently the mottled leaf look isn't affecting the health of it. How would I find out how much calcium is in my water?