RD will grow the fastest at about a little less than 1 inch a month. Tex about the same. The JD about 1/2 inch to an inch (depending on the fish) a month.
My JD actually grows fatsre than my texas. Bought them both one month ago at just over 1 inch and now the gt is over 3 inches and the texas is under 3 inches.
My tex now over a year old has been a fairly slow grower. I'd say around 1/2 inch per month. He is about 7 inches or so now. My current jd has shown a decent rate probably about 1/2 inch or maybe a little more a month. My blood parrots did the same, but they grew in width just as fast as they did in length. I've had them for about 7-8 months and they've gone from 2 inches to roughly 5-6 inches.
the last RD i had grew from about 2inches(the size i bought him) to 8 inches in about 13 months. i had him in a 55 with other fish though so that had allot to do with it i think