morning kikis need more coffee here also
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It's already noon for me and I am still drinking my coffee...morning kikis need more coffee here also

Yes I agree with the previous, you need air intake in the container for the water to flow. You should be able to touch the nipple lightly and see water come out easily.
Here's a video I made of 2 of my youngsters using vertical nipples. You can see the water coming out and how easily it flows, horizontal should be the same.
(don't shoot the messenger) rats could have been coming in and drinking all the water at night.
oops: again..don't shoot me)