Why has the volume of wastewater increased?

you are likely watering when the pot is heavier than it was before... your substrate, as long as you don't alter it, will hold roughly the same carrying capacity of water day 1 and day 100. so if oyu are getting more runoff, that means you are watering at a point which more water currently exists in the pot than before. use weight to trigger irrigation and this should remain more consistent. rate of evaporation is relative to temps and RH.. if these thigns chnaged recently it could impact timing of 'next' irrigation. VPD, also controleld by temp/rh, drives the rate of water uptake in roots. So, if it is drinking slower or faster but you are rigidly watering on a time-based schedule you will need varying amoutns of water to get the job done. it's fine either way... but, if you want to be able to mix nutes with less waste, water based on weight of pot and it will be a similar volume required each time, but the time between may vary... which is less convenient for you? varying time or varying volume of water needed?