if your plant needs to be watered when you flush, it should not show any symptoms of overwatering. if it is, you just need to let it drain and dry. i assume you have good drainage in your pot.
how old is your soil? flushing your soil will not make your soil any hotter than watering it normally. in other words, the more you flush it, the more of those nutes come out with it. if the soil's been in there for some time, chances are that it's getting weaker wtih every watering. this is why not to use nuted soil
just to make sure, you're not watering with nute solution now, right? a plant that size should not have a problem handling nuted soil, but the combination would just be too much.