Hey I started a Coco coir grow and can’t get it past the first week of growth. I’ve tried 3 different times. My grow space has a day temp of 83°F am and 73° pm, 55% Rh, and the lights are on low.
The first 2 times they got thin in the middle around day 5 or 6 and the 3rd time the seeds never came up within 7days
With coco you have to water often. Sounds like you might have been a soil grower previously and are using a soil feeding schedule. If that’s the case you should be good watering at least twice a day. Alternatively you could set up an automatic system very easily and water 5-6 times a day which is more optimal for coco 
How do you know when it’s time to water. I’ve been watering once a day till the water comes out from the bottom. They’re sti in the starter pod. I didn’t want them to be over watered
coco only holds a tiny amount of water solution. Unlike soil where the water gets absorbed into the soil and perlite to be distributed as the plant wants. With coco you can put as much water in as you want but it will just drain. Remember coco is a fibrous plant matter and as such can’t hold much moisture. Thats why you need to water lightly several times a day. Basically just water until you see runoff, then stop and come back in an hour or two. Thats why most people who use coco build an automated watering system with schedule. You will never be able to over water coco.
Is it possible they got thin at the root because of underwatering
I suppose thats possible, did your leaves start drooping and never really get back to normal? is the growth stunted? There’s a ton of variables.
No, they just stretched a little thin go thin in the center and dropped over. The second time it stop growing around day 4 or 5
Almost sounds like dampening off to me? 
It probably was
What do I do to stop that
(#ISearchedIt):
https://www.google.com/search?client=firefox-b-1-d&q=watering+a+Coco+coir+grow
Give enough water to always get at least 10-20% runoff water out the bottom. When growing in coco coir , as a grower you need to provide nutrients in the water . However, nutrients can get built up in the coco if you only give just enough water to wet the medium.
--
--