I the water doesn't 'channel' straight through the soil, a wetting agent (dishsoap) is unnecessary, and don't use it.
Don't let the soil remain wet. Cannabis needs a wet-dry cycle for proper growth.

Once you get your ph test kit, it will eliminate some causes or highlight what's actually going on.

Likely a good idea to get some fresh soil for your next grow. Check with the locals to see what's available in your town. Old, questionable soil just adds to the guesswork of trying to narrow-down causes and effects.

Some fresh pix would help. Old leaves are old news. What's the new growth looking like?