Are the plants you bought non-toxic? Veileds eat plant material...and the insects might nibble on them too.
They need to be well-washed, both sides of the leaves before you use them in the cage.
Here are some sites with good information that you could read...
http://adcham.com/
http://www.chameleonnews.com/
http://www.uvguide.co.uk/skintests.htm#discussion
http://web.archive.org/web/200605020...Vitamin.A.html
Exposure to UVB allows the chameleon to produce vitamin D3 which allows it to use its calcium. Many of the feeder insects that we use have a poor ratio of calcium to phosphorous...so its important to dust the insects with a phosphorous-free calcium powder before feeding them to the chameleon. If your chameleon gets no or little direct sunlight and only gets its UVB from UVB tube lights, then you may want to dust the insects before feeding them to the chameleon twice a month with a phos.-free calcium/D3 powder. Be aware that D3 from SUPPLEMENTS can build up in the system so don't overdo it. The UVB light from either the sun or artificial lights must not pass through glass or plastic.
I dust with a vitamin powder twice a month that contains a beta carotene source of vitamin A. Beta carotene sources of vitamin A won't build up in the system, but preformed sources of vitamin A can. There is controversy over whether any chameleons can convert beta carotene to vitamin A so some people give their chameleons a bit of preformed once in a while. Excess vitamin A can prevent the D3 from doing its job and lead to MBD...so caution is advised not to overdo it.
Gutloading and feeding your insects a nutritious diet is important.
The ADCHAM site I listed above has a well-known gutload in it.
Calcium, phosphorous, D3 and vitamin A all play a part in bone health, etc. so its important to take into consideration any sources of these that are in the gutloading and diet of the insects as well as in the supplements when trying to provide a balance.
Appropriate basking temperatures allow the chameleon to digest its food properly...thus absorb the nutrients in its diet.
Hydration is important too....misting and drippers may be used to provide water. Most chameleons don't drink from a bowl of water....but I have had some that do.
With proper care your chameleon should be with you for a number of years! Good luck!