I'm glad you caught the mold. Don't worry about what other people say especially if its negative you have found the problem and have identified the issue so your birds are safe.
I am happy you shared this with us so others can learn about the dangers of mold and what other products they can use to keep their birds safe.
I've never liked those water containers you have shown as they seemed to build up calcium deposits from our water here on the dish and they felt either scratchy or damaged. Or despite me steaming them with boiling water it felt like the dishes sometimes felt slimy inside which I figured was due to the humidity caused by the container being semi covered.
I bought stainless steel dishes that are easily attachable to the cage with a screw plate and loop bowl/dish holder so its easy for you to put where ever like to place them in the cages.
The only drawback to these types of stainless or crock bowls in the birds can make a mess with them easier by playing in the water or they can easily poop in the dishes.
I like these ones because they lock into place on the cage bars and the bowl slips into it. It makes it hard for the bird to pull the dish out of the ring.
Unlike these hook dishes an inquisitive crafty bird can easily unhook this and dump the entire dish of water on the cage bottom.
Crock dishes are amazing as they keep the water cool in the hotter summer days and they are dish washer safe.
Crocks that lock into place to infuriate your inquisitive craft bird!