Your 80/20 blend with castor is exactly the fuel I've always used for all my engines other than when running in I use the 75/25 mix. If you switch from the 80/20 to the 75/25 then you must retune or the engine will run a little leaner because the extra oil has displaced some of the methanol. Opening the needle (richening) gets you back to having the same amount of methanol going into the engine. It sounds to me that none of the engines were retuned when the new batch of fuel was used and so they all ran lean. Lean is bad but with castor there may not be any permanent damage done. Tuned properly you shouldn't notice any real difference in power between the two fuels.

Don't attempt to run it a bit lean like you said in the last post, open the needle until it's running obviously rich then tune as normal from there. Any time you have a change in fuels, whether it be in oil content, type of oil or nitro then you must retune.