Could this be fertilizer burn?

[BcBerri]

It is a 20-14-13 fertilizer, at full strength (1 tsp mixed with one gallon). I am using 1/2 tsp mixed with a gallon (hence the half strength). This has been slowly happening and getting worse over the past few weeks. And no, this is not varigation. The lighter edges are actually dry and have a damaged consistency. I know the picture I attached to the original post looks like it is all the same plant, but it is not. It is 4 photos of 4 different plants. All bought at different times/stores/ect. It wouldn't let me attache more than one photo, so I had to make a collage. I just found it odd that it was on not just one, but ALL of the plants in this room. I think Ordphien may have some other ideas I hadn't thought about like humidity ect. They are all in the same room together, so same environmental factors. The one phal I don't have in that room isn't showing any of these same signs. Thanks for the input and ideas everyone. I will take a very close look at the care of these guys to see if I can find the hiccup.

[Roey.P.]

One time I found that the store confused and registered strong fertilizer as weak my friend used it and after a day his daisy died all became solid yellow brown. In orchid fertilizers there is more importance to accurate. It can be that your orchid needs really small amounts of fertilize so just add more water.

[silken]

Do these plants sit over a register or vent of some sort?

[RJSquirrel]

"marginal leaf chlorosis" typically caused by a combination of stress factors such as heat, drought, old leaf age and nutritional deficiencies.
A plant lacking magnesium (Mg) may show marginal (on the edges) chlorosis on older leaves followed by inter-veinal (between the veins) chlorosis. Leaf margins (edges) may become brittle and curl upward.

[Orchid Whisperer]

A half teaspoon of 20-13-14 per gallon gives 132 ppm N and 247 ppm total dissolved solids from the NPK in the fertilizer. That's a lot if used at every watering. Might be Less of a problem if used once a month, clean water in between. Another option, use 1/8 teaspoon, or less, per gallon, but use more frequently, every other watering.

[BcBerri]

Thank you for all the responses! I have taken a good look at all aspects of their care for the past few months. I think it is a combo of multiple things. The heat vent is about 6-7 ft above them, so hot dry air. They were moved to this bathroom since it's the guest one and doesn't get used often (so as not to be in the way or disturbed much) which seems to have worked against me. Not enough humidity in a rarely used bathroom. And not diluting the fert. enough. So they have all been moved back to the master bath where there is lots of good humidity, the vent is not blasting right on them, and I am going to cut WAY back on the fertilizer strength. Sometimes the answer is right in front of you and it just takes an extra set of "eyes" to figure it out. Thanks guys!