Odd behavior after vaccines

Ok. I'm 99% sure that I'm overreacting, which I tend to do with my babies. Today, I took my 5 month old Manx and 4 month old long haired tuxedo into the vet. They are neutered and spayed, have had their rabies and are otherwise healthy. Today I brought them in to get their shots. The ones they received are the upper respiratory vaccine(URVC) and feline leukemia vaccine. After they got home, they seemed normal. However, they both started acting very lethargic a few hours later. They have both been drinking plenty of water, but neither seem to have an appetite. Also, neither is responding to playful attempts. Seeing as they are both having near-identical symptoms, it seems like its ok. I'm hoping this is normal with vaccines, but that 1% of uncertainty is driving me crazy. .

[Cliff Redford, DVM]

I dont think youre over-reacting at all. This does sound like an exaggerated response to the vaccines. It is expected that a mild fever and lethargy will occur after some vaccines however if they wont eat then you should contact your vets office. I expect they will recommend you bring them in for a 5 minute visit where they will give something for the fever.
It is not serious or life-threatening but no one likes a grumpy kitty...especially a tuxedo or Manx :)

[ChihuahuaMomx3]

Reading your post about your concern of Vaccines.  Never vaccinate your animal w/ more than 1 vaccine at a time, waiting at least 2 weeks in between vaccinations due to possible reactions.   Reactions to vaccines seem to be more common.  The problem is that when an animal is vaccinated with a series of vaccines example: rabies, Distemper, Parvo in one vet visit ..finding the actual cause & the correct way to treat becomes difficult due to not sure which vaccine actually caused the reaction or sickness.  Vaccinating one vaccine at a time can be more costly unless you have a Vet that agrees to work with you as I do.  My Vet will NOT inject my animal with more than 1 Vaccine in a single visit, due to known issues with vaccine & possible reactions.  It's better to be safe then to lose a dear furry friend due to convenience.    
Hope your kitties have recovered without further issues.