first, was 600mL enough? did you get runoff or can tell entire volume of soil get wet? (10% runoff for soilles / ensure saturation with soil).
If not, correct that bad habit.
So, they are larger and with limited info and no diary i'll assume it's just a bit too dry. they are drinking faser and randomly picking a volume of water to give isn't probably underwatering them.
You can learn how much water it needs in hindsight only... and experience after that can translate if your substrate is made of same stuff as before.. same proportions of perlite or whatever etc...
so, it's good you wait for the pot to get light, then start watering until you get runoff (minimal runoff in soil required and may or may not contain fertilizer, but 10% or more runoff required in soilless while feeding every single irrigation in soilless too.. 1.3-1.5 ec concentration)
You then learn a weight at which you want to use as trigger to irrigate again -- in soil, maybe 1" deep is dry... in coco maybe as the top layer changes color or even before that...
if consistent with weight, it'll require same volume of water to achive appropriate runoff relative to soilless/soil needs. Now you know how much per pot is necessary and can avoid over mixing fertilizer etc.
you can irrigate sooner than these suggestions, but it raises risks of pests and infections... but ppl are successful with multiple irrigations per day - usually have a well-sized pot and soilless/hydro context of course... need some mimimal use of given water before re-irrigation or you will damage the roots. A low water volume capacity substrate with superiour drainage qualities is needed.
You might be fine watering at 50% of weight? depends a lot on what makes up your substrate