need help with progression of fishless cycle

I am on like day 21 or so on my fishless cycle

My ammonia would regulate to nitrite fine but my nitraite seemed to be hanging and my ph was starting to drop, (from 7.0 to 6.8) so I did a 70% water change using API stress coat to treat the water, ( i had my eheim 2227 wet/dry turned off) I added the water to the tank and treated (like i always do)

I did that sunday, my nitrites after the water change were at or about 2.0 ppm (before they were off the chart) ok yesterday moring added 7 drops of ammonia (enough to bring it to around 1 ppm)

checked my water 5 min ago and here are the results:
ph = 6.4
ammonia= .75
nitrites = .25
nitrates = 5.0 to 7.0

what is going on here?

why is my ph dropping?

what should i do?

hurricanejedi said:

I'd get a kH test kit. At the end of my cycle my pH crashed and stalled my cycle for about a week but then it suddenly was completely cycled. If the kH is 0 then the pH will plummet fast and hurt your bacteria. You can then add baking soda to the water to increase the kH.

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i ahve a gh and kh test kit but I misplaced the instructions, i believe that is my prob, ok how much baking soda do i add per gal? i have a 40 gal tank thanks