Advice Needed for C. Macrocarpa & V. Splendida seedlings

[HtownPalms]

I have a few Chambeyronia macrocarpa and Verschaffeltia splendida seedlings thanks to my great palm friend JimmyT! Everything is growing well but lately the palms have started to look a bit tattered. I really want to get these seedlings back to full health before they get too sickly to save. 

First let me start with the indoor environment that these guys have been growing in. I got everything as seeds from Jimmy. I sprouted them using the baggie method in my garage. Once the sprouts start outgrowing the bag I planted them in recycled plastic cups. The cups have 4- 1/4" holes drilled in the bottoms. The soil is mostly volcanic sand with 15% coco coir & 15% topsoil mixed in. I also sprinkle in a little Azomite. There are fluorescent grow lights over them and they get indirect sunlight from a south facing window. They have been in my garage all summer and it is HOT in there. Most mornings my garage is still 85-88 degrees, afternoon its usually 100-104, and my bedtime its 90-94. I water them when the small cups get dry and my finger can't dig down to moist soil. Usually every 4-5 days. I was watering once a week but was losing palms to under watering. 

The V. Splendida are getting brown tips spreading to the rest of the leaf. Even with this its growth hasn't slowed, and otherwise appears to be healthy. 

The C. Macrocarpa are all growing with curled up leaves. I didn't think too much of it, but now they are getting brown tips. 

My questions are:

Are they getting too much water?

Are they getting too hot?

Are they getting too much light? 

Is the curled leaf because of any nutritional deficiency? 

Are ther other problems that i am not thinking of?

 

Here are some pictures of the palm seedlings in question.

[HtownPalms]

I forgot to mention, I also have a small fan that keeps air moving in their area. Nothing very strong, but enough to slightly wiggle their leaves and keep air from being stagnant.