"Number of pellets"
Used the top header on this forum , many helpful things such as nutrition. See there for the 2/3's rule , works for turtles from yearling to juvenile to adult. Your turtles may be a little under one but growing a little too fast by measurements given. Adjust diet. As Steve stated a good well varied diet helps especially as there requirement change to more on the veggie side. By adulthood require 50- 70% veggie and protein only every other day.
http://www.redearslider.com/index_nutrition.htmlAlso look at plant/ veggie links to on what's safe.
Other than adjusting both there diets to prevent problems down the road , nice looking turtles.
Any photo of there setup?
If in same tank now may have to separate once they get older ( sexually mature) or hope both are females with the same personality's . Other combos will need /require separation unless in a large setup for territorial space.