pH question

I Flushed my plants yesterday because the pH was at 7-8! after I flushed I used some pH Down and this morning I checked them and the pH reads like 4-5... Is it ok to just add some pH Up today even though I flushed the crap out of them yesterday and the soil is still wet? also should I add my Nute after I add the pH Up? or wait a couple days?

Aslo, I'm running about 12,900 Lumens for 3 plants in a 2.5' x 2.5' box, is this enough light?

nooooooooo!!!!!!!!!!!!!!!!! flush with the ph that you want your soil to be... so if your growing in soil flush your soil with 6.8 water dont over ph the compensate.thats a bad idea....... flush with 6.8 water