HEY people, ive been doing some research on my plant problem, and im prety sure that ive eigher over watered or over fertilized, any idea's how to solve problem(s)?

If its overfertilized i heard that i need to LEACH the soil, haha dont have a clue how 2 do that?
and if its overwatering i done, how do i solve that?

Cheers.