My Axolotl is refusing any type of Food

Hi everyone! This is my first time posting on these boards so please let me know if I have an error in my post.

I have two axolotls I received on March 31st, one being an albino, and the other is a melanoid. They get along amazingly, never any issues. Both of them are amazing eaters and very healthy, (no curled gills, no curled tail, stomach is as wide as head). I upgraded the pair to a 29 gallon tank on Sunday, October 6th.

The tank was precycled for 5 weeks, and the parameters are as follows:

Temp: 65 degrees (F)
pH: 7.5
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 20ppm

On Sunday after I transfered the axolotls, both ate their worm. On Monday, only the albino ate the worm, and melanoid took it and spit it out, which was extremely unusual for him. Still, he wasn't showing any signs of stress or other abnormalities.

Today is Saturday and he has still refused food. I had a guess that he was constipated, or impacted, since the tank has sand in it now. (It's a very, very fine sand that I asked several opinions from various fish and axolotl experts, I got it at an expo at an axolotl sand. I believe the grain size is 1mm.

I took out my melanoid on Wednesday and put him in a quarantine tub. Later that night when I checked up on him, I found a ton of his sand in the tub as well as a regular sized poo.

I thought maybe he passed it or something, and this time I tried feeding a frozen blood worm cube, to no avail. I've kept him separated and some days he'd pass nothing, and on Friday he seemed to have passed more sand and some sort of stringy substance, but when I did my research it seemed to be some sort of sperm thing. (It looks as if he's reached sexual maturity due to his white fingertips).

I'm unsure of what to do now. Yesterday, on Friday, I offered a cut up worm and he took it and I thought it was all okay! But he spit it out immediately like on Monday. I'm at a loss here, he hasn't looked like he lost weight but nonetheless I'm so worried.

There is an exotic vet near me who looks at axolotls, but I'm hoping to go there as a last resort because it's extremely expensive and I'm a mere college student living paycheck to paycheck. I've attached photos of him, and of the tank.

The four pictures include: my normal tank with my albino, the melanoid in his quarantine tub (who I took a picture of just right now, and noticed there's more sand he's getting rid of in the tank!), and the stringy substance I also just found in there, and another angle of my melanoid.

Thank you everyone for reading this.

Just a small update, my axolotl has not eaten, or shown any interest in food yet. I have him in quarantine, doing 100% water changes daily. I see a little more sand and that clumpy stuff this morning, and did another change. At this point it's been a week since he's last eaten. Should I consider a vet trip? Or maybe someone has some suggestions

I wouldn’t worry too much until he starts showing other signs of abnormal health such as curved gills, curved tail, or blood in stool etc. He looks like he’s a good weight right now and seems pretty healthy looking from the photos. They could be off their game from the tank move, my first axolotl didn’t totally acclimate for 2 weeks when I first put it in its tank. I would just keep offering worms when you can, and begin worrying if you see a lot of weight loss or other symptoms. Keep monitoring you tank parameters and his health but sometimes they just refuse food for an unknown reason, mine does that from time to time. Hope everything works out!