As you said above u have 73 yellow herb leaves which is good however for another reason, yellow herb leaves are what you double click to heal your pets helf because some mobs of monster do attack your pet.
Now onto how you feed you pet, Its prity simple really i have a lvl 6 hatchling
(works for ponies aswell) i tend to feed it quality stones which you can get by using a tool aid on a hammer or pickaxe which you can buy from merchant geres or other players then go to the mine east of the north gate.
There is another way! you can just buy quality stones from players however,
they are around 1k each! so if you fancy some mining xp and the slightly cheaper way go don it your self and f your rich go buy some thats what i do :P
Just make sure your pet is out and then just double click on the herb in your inventory and it is immediately applied to your pet. For food get Quality stones and same thing, make sure your pet is out and just double click on the quality stones in your inventory and it is immediately applied to your pet.
And the best herbs are the green herb - get more for each than yellow. Best to get a tool-aide and you will only harvest for a minute and will get 27. The tool is destroyed but its worth it- otherwise you spend all day harvesting to get as many.
Same with quality stones - get a tool aide - I get a good number of them in drops, and you will get 27 quality stones.