Yearling buck not eating and laying with nose in ground

I have a Yearling 8 point. Still in velvet as of Sept 7th. He has not been eating for the last three days. Temps have been in the 90's in Central, IL. Now temps are rain and 60's he will not get out of his bed and is sitting with his nose to the ground. Slight foam around his mouth, and his nose has green dryer boogers. He's Acting sluggish and off balance. He seams to keep getting worse every day.

He gets fresh water every evening and ADM deer feed, some corn, some grain oats, assorted bird feed, 6 slices of bread and 2 potatoes every evening. He has clover, chicory, orchard grass and random weeds in his pen. Over the last 3 weeks I have weaned him off shock effect probiotic. Also I have been adding a cucumber or 2 to his food each day for the last week and a half.

Could this be bloat or something from the cucumbers?
Or a EHD issue?

I just went out to pen to hand give him some water and clean his nose and mouth up. I finally irritated him enough that he stagnated to a stance and his head was hanging down and to the left. He won't move it right. It kind of looked swollen on the right side but may have been cuz it was turned so hard to the left. He is also very wobbly.

Help!!!

I took in a stool sample to vet, waiting on results. He was thinking possible parasites, is this possible even though the buck looks thick and health?

It was EHD

Breathing was about normal, stool sample was fine, heart rate and temp were elevated. Lips and tongue started to swell Saturday. Vet came Saturday morning and thought it looked like a virus(EHD). He was given steroids/ anti inflammatory and long lasting antibiotic. By Saturday night he couldn't stand and died early Sunday morning.

Thanks for the replies, it was difficult to see my baby boy go down. There is a lost going through my head right now.

In the future what is my best way to battle EHD? I only have a hand full of deer. Do they make a 10 dose bottle of vaccine instead of a $500- 50 dose bottle? Does the vaccine work good and cover most strains of HD? Would spraying pens in and out with insecticide help? Would keeping all grass short help? Usually I let 25% of pen grow up in weeds/switch grass.