Frosty melons

Experiencing what seems to be my first nutrient lock out. Bought a soil ph tester from homdepo its reading 7.0 so that what bring me to that conclusion on top of the slower growing and the slight yellowing around the leaves. I was being cheap and using the liquid ph tester that comes with the ph up and down and im regretting now seeing my plants in not the best condition. Im ordering a better ph pen today i used the vivosun one the i currently have got the water to 5.8 checked the run off and its at 6.2 hopefully that helps. Saturday im going to top dress and water at 5.8 aging and im thinking that should put me back on track Any advice i could definitely use some tips and pointers or advice