2nd Grow, 1st was carnage

I'm kind of thinking my UK Cheese is near harvest, so have started flushing with 1ltr of water, about every 48hrs. The other two am continuing to feed and water. I have now installed a greenhouse heater to maintain a better temperature, although waiting on thermostat to arrive. Have noticed that other growers who use Lemon Kick only use less than 1ml but I seem to need a lot more? Am assuming that is because my tap water is harder...? or is it the nutrients...? So was doing a bit of reading last night, and came to the conclusion that I should probably water the other two without nutrients as I've probably got a build up of nutrients. So, I don't have any scientific evidence that makes me think I should do it, "I got a feeling" (lol), which is what I had on my first grow.....:(. Anyways, irrigated the Amnesia as the pot was feeling light. Northern Lights was still heavy so have left it. Probably give it a litre tomorrow. I reckon the Cheese is ready to harvest (guessing), but think I should wait until the soil has dried out..... Or do I cut now????