I have a freshwater planted 55 gallon fish tank , I use RO water which as you know take good and bad minerals out of the water. I put good minerals back in for my plants to use to grow.

I also have a 29 gallon tank with just fish, No Plants, just freshwater fish. I used RO water since I have it, Just wondering if I should, have to, or highly recommeded to add the trace minerals into the RO water? And if I should even worry about PH. The fish seem happy.

I have been adding RO water to this tank , with no trace minerals and no PH. Just wondering if that's okay? or if it needs minerals PH etc.

Yes you still need to add the minerals back in - fish need them to grow & function properly.