I have tested my water a few times for the pass few weeks for ph, ammonia, nitrites, nitrates, kh and gh and the results are:

ph - 5.5 to 6
ammonia - 0 mg/L
nitrites - 0 mg/L
nitrates - 5 mg/L
kh - 10 mg/L
gh - 20 mg/L

Water changes are made 3 times a week with 24 hours mature water that have a ph of 6.8. My question are why do the ph drop so fast? Is it because I have driftwood in it? Or is it because my kh and gh is too low to buffer and I got a ph crash? Do I need to add some "ph up" from the lfs?

From the test results, does it look like I have a healthy bacteria colony in the filter? My guess is "Yes" but I need to know for sure.

My last question is, with the present results, would discus be happy in it or do I need to do some changes?

Thanks in advance.

Frankie