Water heater not putting out water

We had water that didn't get blown out of our water supply lines the winter before last and burst the pipes. I was really sick last with my pregnancy last summer and we didn't camp and the camper sat fallow all last year. So this year I decided rather than trying to repair the split cpvc pipes where they were split, to make the leap and replace all the supply pipes in the camper in Pex with the crimp style clamps. I basically duplicated the cpvc plumbing layout exactly in the Pex. This was my first experience in Pex and I got it all done with no leaks this weekend while camping and in between nursing my 5 mo old. Go me! :)

So, all the Pex was leak free, but one of the female, hand tighten, screw type connections coming off the water heater on the hot water, out line that screwed into the Pex had a tiny drip. When we went to turn on the hot water, it came out rusty looking with lower pressure than the cold, then went down to a trickle then a drip. If I turned off the spigots, when I turned them back on, I got a trickle then a drip again.

Any ideas what is wrong or how to trouble shoot it? The cold water is fine, high pressure. Could it be scale or rust from the water heater blocking the out line? Or is it something else? If its scale, how do I clean/flush it out? Are there directions on the web?

Thanks!

PS I can get pics and brand name if needed. But I am inside nursing the baby, so JLMK if you need it. Its the basic RV water heater that came with the TT with a switch on the front of the sink to ignite it. When I realized there was no water coming off, I turned the water heater off immediately in case there was no water in the water heater tank.