Hi,
Have you written your code in stages.
Have you code that JUST reads the DHT, AND works?
Have you code that JUST reads the moisture sensor, AND works?
Have you code that JUST activates the relays, AND works?
Until you can establish this, your code could have many problems.
BUT a schematic in this case is essential.
Links to sites where data/specs are of your hardware would help too, especially the relay.
Thanks.. Tom... 
