The familiar food should still be offered to your chinchillas from step 1 to step 4. In addition, you start integrating new components into their bill of fare. Don't get unsettled by all the
warnings on the internet: Most chinchillas will bear a food change without any problems, even if carried out quickly.
The following sequence has therefor been proven as gentle and reasonable:
Introducing a mix of dried herbs, leaves and blossoms, barks, twigs and roots
You can introduce these components quite quickly and soon "ad libitum" (= at will, unlimited), and you need not introduce them sort by sort, but may offer a mix from the beginning. That mix might for example contain the dried leaves of: dandelion, stinging-nettle, girasol, echinacea, various berry bushs, narrowleaf and broadleaf plantain, aswell as willow tree bark, calendula, gingko leaves, green oat, hibiscus blossoms, peppermint, apple tree leaves, dandelion roots and nettle roots.
In the end, you should feed them a mix of 30 different plants. Beginners can buy a ready-made mix. You can find some examples here:
Introducing fresh apple and fresh herbage
Introduce one new sort of fresh food per day, plus continue offering those which you have already introduced. For example, if there were no problems with chiccory on one day, offer it again the next day and in addition offer one new sort of fresh food.
Quantity: At the beginning you give them e. g. only one little piece of apple (the size of a hazelnut), one or two dandelion leaves, or one little twig with two or three leaves on it. In succession, you raise the quantity, until one day they will leave a bit of it over. Ideally, you should offer several different fresh foods per day.
The following fresh plants are especially adequate at the beginning: apple, calisia repens, chiccory (being a natural helper to build up the intestinal flora, ideal for a food change), dandelion (plus the blossoms), plantain, lettuce, girasol leaves, sun flower leaves, basil, twigs of cherry tree, hazelnut tree and all other fruit trees and willow tree, etc.
Introducing further sorts of fruit and vegetable
Proceed identically as on step 2.
Be careful with potentially flatulent plants like clover, bur-clover or cabbage! Use them only at the very end of the food change and never combined with any pellets or other compound feeds!
At the beginning, we can recommend: for example bananas, pears, romaine lettuce, or carrots (plus their leaves).
Pure oilseed mixtures are usually easy to digest and can slowly be integrated into the bill of fare. You need not necessarily introduce them sort by sort.
You can find some examples for ready-made seed mixtures here: www.chinchillavermittlung.com/t4356-bezugsquellen-fur-fertige-fur-chins-geeignete-samereienmischungen
Seeds are a concentrated food, not a main food! The quantity you may offer daily differs from critter to critter. Some chinchillas may be given seeds ad libitum, for others you must ration them to one or two tablespoons per day and chinchilla. You might as well offer only small portions of seeds once or twice a week (as a special treat or supplement), in case you offer pellets as a concentrated food. Or you can mix together seeds and pellets and offer both daily.
When introducing seeds into the bill of fare, you slowly increase the daily amount of seeds that you mix with the old kind of concentrated food (usually pellets).
Omitting compound feeds
Either your chinchillas will slowly stop eating the compound feeds on their own terms. Or, if you like, you can quit offering them, as soon as all the new food components have successfully been introduced and the chinchillas have got used to their new diet.