New at this

I’m in a wheelchair using a grow box that is sat on my ground. I transplanted my 5 sprouts 2 days ago and they are growing now. Today I have to adjust my PH as needed. I was wondering if there is an easy trick or process to fixing the PH without having to pull the plants out and disconnect the filter to the reservoir? If not, what should I out the plants in when I do this? Also, when I change my water, where would I put my plant while I do this?