I know how you feel about getting two adorable baby veileds, but I don't think much of the person you bought them from for letting them go at such a young age. There is a natural mortality rate in very young veileds (and other species of chameleon as well) and I don't think they should be sold to people at such a young age. That being said, you now have them and I hope they will be two of the lucky ones and do well for you.
I'm glad you have already been reading about them... ...but please read everything that you can about these chameleons ASAP. Chameleons are not easy lizards to keep...especially for a first lizard pet.
Could you describe their setup please...including their feeding and the lighting and supplementation please.
You said..."What I was wondering is if anyone has any valuable information that they (unfortunately) had to learn the hard way when they started out with chameleons"...I'm always glad to pass on any information that I can about chameleons. I like to see people keep them successfully....but there is so much to tell you....the following is only the tip of the iceberg.
One of the main problems that you have to watch out for with veiled chameleons is the development of MBD (metabolic bone disease). It is caused by imbalances in their nutrition and husbandry. Calcium and vitamin D3 and vitamin A are three of the main "players" in the imbalance. Lighting plays a part in this because it takes natural sunlight (not through glass or plastic) to allow the chameleon to form vitamin D so that the calcium can be used. If the chameleon isn't able to be in natural sunlight because you live in a climate where the chameleon cannot live outside, then UV light must be provided and sometimes even vitamin D3 supplementation is necessary. The temperature in the cage plays a part too, since chameleons need heat to allow digestion to take place (since they do not produce their own heat). Feeding appropriately sized insects that have been gutloaded and dusted with supplements is important. The D3and calcium supplement regime depends on whether your chameleon is exposed to sunlight or not...but vitamins and minerals are sometimes needed too. Vitamins A and D3 can be oversupplemented, so should be given with care.
Stress plays a big part in the health of a chameleon....so they are often thought of as a look-don't touch type of pet.
Baby chameleons can dehydrate and overheat quicker than adults, so I always keep their cages at a more moderate temperature than is recommended for adults and mist them more often.
They should be housed individually after the age of about 3 months, IMHO. I don't let my veiled chameleons breed until they are over one year of age. (Why put additional calcium demands on a creature that is still forming its own bones?)
Once the female is over three months of age, I provide a container of sand in her cage so that if she produces eggs she will have a place to lay them. Female veileds can lay eggs once they are sexually mature (at about 5 months of age) even when they haven't been mated. Not giving them somewhere to lay them, can lead to eggbinding.
Let your chameleons walk off the branch onto your hand if you have to handle them. Pulling them off a branch can cause damage to their legs and/or tail if they are holding on tightly.
Hydration is important. Misting the cage with a fine mist can be done several times a day. I don't allow the water to pool or form large drops since baby chameleons can aspirate it. The water should be warm.
Enough for now. If you have any other questions, just ask.
I will post a second message with some sites that you might want to read.
Good luck with these two tiny creatures!