I'm sorry to hear about you're struggles as a new beardie owner. I too just adopted a second beardie and would be worried sick.
Vomit is concerning but you have to be sure it is vomit (make sure it wasn't a poo!) , and make sure it doesn't happen again. Check on the water a lot, and change it often.
Stress marks is a new one, but bearded dragons have striped patterns on their bellies.
I would suggest making sure your dragons schedule is exact. (My dragons know when to go into their home for bed and when their food bowl is about to get filled) My beardie goes from her basking area into her hide at 6 every night. She wakes up right now at 5
Give your dragon an hour or so to wake up in the morning before bothering them. After an hour give them a diverse selection of greens. Currently our two eat turnip, mustard and collard greens with butternut squash and green bell peppers. These are all high in nutritional value for our friends.
Make sure protein is a 2-3 times a week thing. I would also suggest finding a bigger perch for your beardie that is closer to their heating lamp. With options, a high perch, and area they can hide under and an area in the middle.
Winter time lights should be 10-11 hours and Summer 12-13 to mimic what is in nature.
Especially for an adult dragon, eliminating cricket may be your best bet. Superworms and hornworms as a treat would be ideal. Crickets are low in any kind of nutritional value for them.
You definitely have enough space but filling the space can help with small dragons from feeling anxious with so much area.
If you are still worried and the symptoms get worse of an overly anxious dragon, an exotic vet will always help. Yearly check ups are always good for any pet.