Indian Ringneck. Chick 2 of 3 very small

Hi. My Indian Ringneck pair have successfully hatched 3 eggs (clutch of 4). Babies are now 24 days old. Two of the chicks are a good size and are starting to feather. The third is substantially smaller. (About the size of a 8 day chick).

The parents are eating well - spinach , bok choi, carrot, corn and sprouted seeds + premium seed mix + pellets. I have tried them with other fruit and veg as well as cooked egg yolk and egg and biscuit etc without success.

My strategy at the moment is to leave the chick with the parents and make sure they have plenty of good food to feed out. I am concerned my strategy won't be enough and more intervention is required ?

I am also worried as the size difference increases the little one may not get a look in for food? I check the chicks on e a day and all have full crops. I do not have a brooder box and I am reluctant to interfere on the basis the parents are better at this than me.

Should I consider supplementary feeding the chick for 1 feed a day? Will this cause digestion issues between commercial mix and parent food? The chick is bright and walking etc - just very small. Hope someone can offer some advice from previous experience.