You do know that chameleons puff/bulge their eyes up when they are cleaning them, don't you?
You said...you use "wood chip bedding"...some woods (cedar, pine, for example) contain oils that are toxic to chameleons. Many substrates will stick to their tongues and end up ingested and in many cases cause impaction...so I use no substrate with my chameleons.
I usually use pothos with all my chameleons or some other non-toxic plant and make sure that I wash it well (both sides of the leaves) before I put it into the cage. I also cover the soil so they can't eat it (either by accident or on purpose). IMHO the plants for any chameleon should be non-toxic in case one of the insects chews on it or the chameleon ingests some of it. Veileds, being omnivores when they are about 6 or so months old often eat the leaves and will also eat greens and veggies and fruit.
You said..."I take them outside daily for UVB exposure, usually between 15-45 minutes"...even though they are out daily, it still wouldn't hurt to have a UVB tube light over the cage. Light from the sun or a UVB light shouldn't pass through glass or plastic BTW.
You said..."i dont know exact temperatures but i use a 100 watt ceramic heat emitter and a 150 watt basking lamp"...being heliotherms, its questionable as to whether sunloving chameleons recognize that a ceramic heater is a source of heat....and its important to know the temperature of their basking area and the ambient temperature of the cage.
You said..."I do gutload my crickets with a formula and available vegetables i have around the house"...I don't use commercial gutloads because it makes it more difficult to control the balance in a chameleon's diet, IMHO.
Balance of calcium, phosphorous, vitamin A and vitamin D3 are important (as well as appropriate basking temperatures) in bone health. Imbalances can lead to MBD (metabolic bone disease). Most insects have a poor cal./phos. ratio so its important to dust the insects with a phos.-free calcium powder before feeding them to the chameleon at most feedings.
I dust with a vitamin powder twice a month. I use one that has a beta carotene source of vitamin A because it won't build up in the chameleon's system. Preformed vitamin A will...but there is some uncertainty as to whether chameleons need some.
I also dust with a calcium/D3 powder lightly twice a month....but my chameleons don't get exposure to sunlight as a rule. D3 from supplements can build up in the system, so its important not to overdo it.
You asked...."I just realized the supplements I am dusting my crickets with are expired, actually in 2000 when I last had chameleons. Could this be my problem?"...I can't give you a proper answer on that. I'm not sure how age of the supplement would affect the nutrients in it.
You said..."They seem to be growing less and less active"...at their age, they should still be growing and should certainly be active...so if its not a husbandry issue that you can solve quickly, then I would recommend that they go to a vet.
The following points have nothing to do with the eyes, but are important in keeping chameleons...Are the chameleons housed in the same cage or can they see each other? Its okay for the first few months (no more than 5 or so) unless they show discomfort with it or one is growing more quickly than the other.
When the chameleon is 6 or so months old, its important to provide an egglaying site for egglaying females because veileds and some others can lay eggs even without being mated.
Questions...what species were your last chameleons and how old did they live to be?
The way I keep chameleons may not be the right way or the only way but I have been keeping chameleons for over 20 years now (geesh, am I really that old??) and my veiled females generally live to be over 6 years old...so I must be doing something right!
The climate you live in may be different than mine too and may require alterations to the husbandry. I live in a climate where the winters are cold and the summers are not often as hot as some chameleons would like.
Sorry this is so long...but I like to provide as much information as I can because I hate to see a person lose a chameleon!