Weak chick and no heat through night

[Cierabug]

When I woke up the heater that the I had set up for my 4 day old chicks was cold and the smallest chick was snuggled by the bottom of it and Im not sure if he hit crushed at all. I warmed him up inside but he's acting very weak as if he just hatched,has very visible veins in his legs and won't eat or drink.He recently started making noise and moving again but still keeps his eyes closed and won't stand.
I was already keeping an eye on this chick because he was smaller and not growing feathers as fast as the others. He also has some dried yellow/brown stuff near over his belly button, but because of a problem with another chick dieing from having his umbilical cord messed with I don't want to clean it. His vent is clean though so he can't have pasted butt.
This is my first time incubating chicks and this is the chick I had planned to keep as a pet so I really dont want to have to loose him or put him down.

 

[le_bwah]

Sometimes weak chicks don't make it, but I wouldn't give up on them. What type of heater are you using? Could you post pictures of the chick? It would help to see what you're seeing.

 

[AlleysChicks]

The yellow brown stuff is probably yolk that wasn’t absorbed. Leave it be and it’ll dry up and fall off on its own.

What kind of heater are you using? They should have a warm side and a cooler side to go to if they get too hot.
Keep him warm. Offer warm water with electrolytes to him so he gets warmed up from the inside too.

 

[Cierabug]

The only area where they would be safe from animals was a shed so I used milk jugs filled with hot water with fleece around it to use as a cave to trap heat. It gets 80-90 degrees where I live so I thought it could work.
The connection here isn't that great so the photos won't send sorry

 

[chickens really]

Chicks really require heat the first few days and extremely important...then they can handle drops in temperature..

 

[Cierabug]

Him and all of the others had been doing good so far but the fleece blanket that was supposed to trap in the heat got pulled of somehow last night and the bottle was cold.Hes 4 days old and the rest of his sibling are 5 days old, so I thought he was smaller and not as active because he hatched late and was kinda stressed out due to me having to be in and out of the incubator he was drying off in when the other late hatching chick stopped doing well and died

 

[chickens really]

Heat lamp is needed...

 

[Cierabug]

Heat lamp is needed...

I'm already planning to isolate him and put a heating pad in his cage, do you have any advice about how to get him to dr

 

[chickens really]

I'm already planning to isolate him and put a heating pad in his cage, do you have any advice about how to get him to dr

Drink?...Peep and dip his beak into the water the first time..

 

[Cierabug]

Drink?...Peep and dip his beak into the water the first time..

Sorry I ment to put drink and eat but it accidentally sent early then crashed.
He doesn't seem to want to drink or eat. I've dipped his beak in water and showed him were the food is but he just keeps trying to sleep
Also his poop is mostly white with small amounts of brown and it's been either been liquidy or foamy/bubbly