It looks like the developer is not warm enough to me. Check to make sure it is about 32 degrees celsius. You will probably have to adjust the iris after increasing the temperature.
If you have the metal tank heater. The heating circuit is incredibly simple. If your heater is not heating first check all connections, including those inside the junction box that the heater and thermostat plug into.
If you have heat belt system. Check connections at temperature controller box.
Let us know how that works out for you.