B. Cucullata concerns (sunburn? root rot? light deficient?) and other misc. questions

[saxxophone]

Hello! This is my first post on an orchid forum so apologies if I'm in the wrong place. I am a novice orchid grower; I have five orchids that I've attained and managed to keep alive since last March. My most recent purchase is a young mounted Brassavola Cucullata that I got from Andy's Orchids during one of their sales. This morning, I noticed one leaf that's beginning to yellow, and is now black at the tip. I've also noticed two leaves next to it that are starting to yellow at the tip as well.

I've had this orchid for about two weeks now. Since it's mounted, it requires watering more than once a week, so I've been watering the media every night, or once every two days; essentially letting the media dry out completely before watering again. I've also been wetting the roots along with the media, but I understand now that I shouldn't be watering those roots as often since it could lead to rot. I'm also planning on watering this orchid with warmer water, as I've read that it may be better for this orchid species. Lastly, I used to use the MiracleGrow Orchid plant food mist in the past, but have since moved to the RepotMe 13-3-15 as of a week ago; I've been using this fertilizer weekly as recommended.

As for lighting, I use a 5Watt 3-level led grow light that I purchased on Amazon; I keep it on the highest level for 10-12 hours a day. I admit that last night I accidentally left it on for 14 hours, so I'm curious if this dying leaf is just an aging leaf that's running its course or if it's legitimate sunburn. Lastly, I keep my apartment between 69-73 degrees Fahrenheit. I also try to keep the house fan on the majority of the day to help circulate air throughout the room.

In addition to my Brassavola, I also purchased a mounted Cattleya Luteola which has been doing pretty well. I have a phalaenopsis and a dwarf phaelanopsis which I've had for almost a year now, and a Dendrobium Thersyflorum which I bought a couple months back. I admit that I've seen no new growth in the D. Thersyflorum, and minimal growth in my phaelanopsis orchids over the course of the past 1-2 months. I understand the P. Thersyflorum is about to start a hibernation until January/ February, but I thought I would see at least some sort of new growth before then. I'm curious if I'm not giving these orchids enough light, or if it's a fertilizer issue.

TL;DR here are my questions:
- Is this leaf sunburnt? rotting? dying from age? not enough light?
- Is my light source giving off enough light? too much light? What led lights would you recommend?
- Any tips to better my watering routine?
- Why do you think my orchids aren't growing any?

I'm open to any feedback; I just want to better my routine for my orchids. Thank you!

[Roberta]

That Brassavola cucullata can and should be thoroughly watered daily, every 2 days at the very least. You can't overwater a mounted orchid like that. It may be reacting to lack of water - if it is insufficient, it will drop leaves to cut down on water loss through transpiration. The Den. thrysiflorum won't do much of anything until spring, except maybe for dropping some leaves (it may or may not, but definitely this is getting to be nap time not grow time. You should not totally stop watering, but you can cut back. Fertilizer is the the least important factor - the Den should not get any until new growth starts, the others will eat less as the weather cools and days shorten.

Also, orchids don't do anything fast... 1-2 months is nothing in the growth cycle of an orchid.