One I can tell the colours on?
JBL and Sera were mentioned locally here in a similar discussion. I canít really comment as always used API mainly.
Ph using api, meters, pool kits - generally all same.
A pool kh
test kit might be better as more accurate reading needed.
For nitrates, even the expensive $200 farm test kit is +\- one reading. As long as trends make sense.
Api phosphate seems ok.