My hamster is scratching a lot and losing his fur. What could be causing this?
There are several possibilities for fur loss amongst hamsters. Often these little pocket pets develop allergic reactions to the shavings used as bedding in their cage. Cedar shavings are more irritating than pine, and dusty shavings of any kind make for poor bedding. Try eliminating all shavings and providing cotton baton for a bed with only paper towel as a substrate. You can shred some paper towel to provide privacy and softness.
External parasites, skin infections and certain internal disease can also cause fur loss, especially when accompanied by scratching. Make sure to visit your veterinarian who can check for these possible causes.

Lately I have noticed that my guinea pigs incisors do not line up, and as such he has trouble cutting his food, especially harder vegetables and the like. I feed him by hand. Is there a solution to this problem? Will it fix itself with time?
Your guinea pig's teeth problems are a common affliction not only to guinea pigs but to rabbits as well. To answer your question:
1) No, this problem does not fix itself with time. In fact, it often intensifies and has to be addressed more often. You should treat any eating disorder with urgency, as your guinea pig will suffer from hunger and weight loss.
2) Is there a solution? Yes, we regularly cut or file teeth that overgrow (although in actual fact the tooth is growing normally, it is just not being filed down normally). In the meantime, cut up your cavy's harder foods like his vegetables and other foods that are too hard to break. You may even want to soften some pellets with a bit of water. When you have your guinea pigs incisors verified it would be important to have his molars checked at the same time. Malocclusion can affect all his teeth.
A permanent solution involves surgically removing the front teeth altogether, but be sure to talk about all the pros and cons with your veterinarian that specializes in exotics.