note: a piece of pumpkin candy filled the lump's growth bar by about 3%

feeding lumps 10 1* creature foods gave them an average of 5% growth per food.
6.72% for 2* creature foods
8.28% for 3* creature foods
10% for 4* creature foods
2.5% for sparkling water
6.64% for pumpkin pies
4.14% for parfaits (parfaits still less growth than pumpkin pie? i guess it's 3* vs 5*...)*
5.84% for mixed nuts. this would mean that a cat has 3.75 times the growth time of a lump! yay!

new numbers for parfaits and pumpkin pies have been unlocked as i took 2 lumps and fed them parfaits or pies until the growth bar was nearly full. these numbers are:
pie: 17 pies, 5.84% per pie (looks like my original number was somewhat off...)
parfait: 24 parfaits, 4.17% per parfait (roughly the same number as in the previous test phew)
and yes apparently mixed nuts have exactly the same growth as pumpkin pies.

...i think the bar may be 128 pixels long instead of 134 actually. changed the values to go with that!!
^ the bar is very likely 128 pixels btw.

also, it looks like charms trigger before mirrors activate puzzle boxes. a charm gives your pet some affinity at the end of the day and mirrors+puzzle boxes can increase the affinity the charm just gave. neat.
and, charms seem to trigger before the evolving process checks the affinities. convenient

* even though you could feed a pet more parfaits than pumpkin pies before it grows up, the power gain from pumpkin pies is so large that, if you feed one pet pies and one parfaits every day, the pie pet would end up with more power. (source: i did that with 2 lumps (forgot to feed both of them on one day tho but that shouldn't affect the result too much right?) and pie lump came out with 45 prima when released while parfait lump got 32.)