Soil PH Problem

I think my soil has a pH problem, because my plant has been suffering alot and not growing good AT ALL. Ive tried to figure out what could be the problem but still no luck. I think ive narrowed it down to the soil. Heres some problems ive been having.

very slow growth
leaves curling downwards
white spots on tips and along veins of leaves
Small leaves
Weak roots
Water retaining in soil for days

I think all of these can be related to the soil. What should i do to my soil to help my plant out before it dies.

ive did some reading about nutrient difiscencys and i read about zinc. Zinc seems to be one of my big problems because white spots on leaves and in veins is a major sign. Also the twisting of leaves ( which is happening on my newly developing leaves ) is another sign. How could i increase zinc in my soil or plant?