Hello William,
First question I have is how do you kn ow the
pump is adequate? GPH has very little to do with a pump being adequate. Second is I'm a bit confused by your diagram. Is the water feed ling going through the bottom of the buckets?
Lastly, according to your diagram you have three vertical feed lines. One going to each bucket. That may very well cause a problem, especially allowing air to get in the feed lines.
If it were me I would have the main feed line (one line) coming from the pump pumping above the buckets. Then running the three feed lines to each bucket from above. So instead of having three tubes trying to pump water up fighting back pressure in all three tubes. You only have one tube going up hill, and gravity feeds/flows downhill to all three buckets. Eliminating the possibility of pressure equalization issues and air getting into the lines.